Packages & Modules - GopherCon Poland 2019

Transcript

1. Packages & Modules GopherCon Poland, Gdansk, June 27 2019 Oleg Kovalov Allegro https://olegk.dev
2. Agenda Packages & Modules
3. 3 - About me - Packages - Modules - Summary - Q&A
4. 4 - About me - Packages - Modules - Summary - Q&A Interfaces
5. About me Packages & Modules
7. - Gopher for ~4 years 7
8. 8 - Gopher for ~4 years - Open-source contributor - Go-critic - static analysis tool - Go-advice - list of Go tips @ GoGoConf 2018
9. 9 - Gopher for ~4 years - Open-source contributor - Go-critic - static analysis tool - Go-advice - list of Go tips @ GoGoConf 2018 - Engineer at allegro.pl core team
10. - Gopher for ~4 years - Open-source contributor - Go-critic - static analysis tool - Go-advice - list of Go tips @ GoGoConf 2018 - Engineer at allegro.pl core team Website: https://olegk.dev Twitter: @oleg_kovalov Github: @cristaloleg 10 Twitter & slides
11. Packages Packages & Modules
13. - Short and clear 13
14. - Short and clear - May be abbreviated when the abbreviation is familiar 14
15. - Short and clear - May be abbreviated when the abbreviation is familiar - Abbrv name is easy to understand 15
16. - Short and clear - May be abbreviated when the abbreviation is familiar - Abbrv name is easy to understand See standard packages for good examples - io (input and output) 16
17. - Short and clear - May be abbreviated when the abbreviation is familiar - Abbrv name is easy to understand See standard packages for good examples - io (input and output) - strconv (string conversion) 17
18. - Short and clear - May be abbreviated when the abbreviation is familiar - Abbrv name is easy to understand See standard packages for good examples - io (input and output) - strconv (string conversion) - syscall (system call) 18
20. - If abbreviating is unclear 20
21. - If abbreviating is unclear - If name is ambiguous 21
22. - If abbreviating is unclear - If name is ambiguous - snake_case or camelCase 22
23. - If abbreviating is unclear - If name is ambiguous - snake_case or camelCase - psdb (Postgres? Parallel search?) 23
24. - If abbreviating is unclear - If name is ambiguous - snake_case or camelCase - psdb (Postgres? Parallel search?) - srv (service? server? surviving?) 24
25. - If abbreviating is unclear - If name is ambiguous - snake_case or camelCase - psdb (Postgres? Parallel search?) - srv (service? server? surviving?) - buf (buffer? buffer what? WoW buff?) 25
26. - Avoid giving a package a name that is commonly used in client code 26
27. - Avoid giving a package a name that is commonly used in client code - buf is a good variable name for a buffer - the buffered I/O package is called bufio (buffer + io) 27
28. - Avoid giving a package a name that is commonly used in client code - buf is a good variable name for a buffer - the buffered I/O package is called bufio (buffer + io) - client is a good name for...client - but not a package name 28
29. - Avoid giving a package a name that is commonly used in client code - buf is a good variable name for a buffer - the buffered I/O package is called bufio (buffer + io) - client is a good name for...client - but not a package name - imagine a replacement for it 29 c ? clnt ? cli ? clientHTTP ?
31. These std packages are a good names thiefs: - path - path/filepath - net/url And you cannot use your variable url easily, oh :( 31
32. 32 These std packages are a good names thiefs: - path - path/filepath - net/url And you cannot use your variable url easily, oh :( But there are good examples: - strings - bytes - net/urls instead of net/url looks good enough
33. Most of the projects in Go are flat and this is fine 33
34. Most of the projects in Go are flat and this is fine - Try to keep it clean github.com/foo/bar/pl/goava/src/main/code/go/validation 34
35. Most of the projects in Go are flat and this is fine - Try to keep it clean github.com/foo/bar/pl/goava/src/main/code/go/validation - Avoid do src/ or pkg/ (in most cases) gitlab.com/foo/bar/pkg/process 35
36. Write shy code - modules that don’t reveal anything unnecessary to other modules and that don’t rely on other modules' implementations. --- Dave Thomas (with Andy Hunt, he co-authored The Pragmatic Programmer) 36
37. Write shy code - modules that don’t reveal anything unnecessary to other modules and that don’t rely on other modules' implementations. --- Dave Thomas (with Andy Hunt, he co-authored The Pragmatic Programmer) And shy also means: 1 package = 1 thing 37
45. - Organize by functional responsibility 45
46. - Organize by functional responsibility - Don’t put all the type into models package 46
47. 47 - Organize by functional responsibility - Don’t put all the type into models package - Keeping them in one gives nothing
48. 48 - Organize by functional responsibility - Don’t put all the type into models package - Keeping them in one gives nothing - In the end this will be a spaghetti code
49. 49 - Organize by functional responsibility - Don’t put all the type into models package - Keeping them in one gives nothing - In the end this will be a spaghetti code - (The same applies to the interfaces, implementations and so on)
50. 50 . ├── app ├── cmd │ └── <project-name> ├── blog ├── comment ├── mock ├── pkg │ ├── superpay │ └── validation ├── store │ └── postgres ├── user └── <project-name>.go
51. 51 . ├── app ├── cmd │ └── <project-name> ├── blog ├── comment ├── mock ├── pkg │ ├── superpay │ └── validation ├── store │ └── postgres ├── user └── <project-name>.go
52. 52 . ├── app ├── cmd │ └── <project-name> ├── blog ├── comment ├── mock ├── pkg │ ├── superpay │ └── validation ├── store │ └── postgres ├── user └── <project-name>.go
53. 53 mock.NewBlog(...) . ├── app ├── cmd │ └── <project-name> ├── blog ├── comment ├── mock ├── pkg │ ├── superpay │ └── validation ├── store │ └── postgres ├── user └── <project-name>.go
54. 54 . ├── app ├── cmd │ └── <project-name> ├── blog ├── comment ├── mock ├── pkg │ ├── superpay │ └── validation ├── store │ └── postgres ├── user └── <project-name>.go
55. 55 . ├── app ├── cmd │ └── <project-name> ├── blog ├── comment ├── mock ├── pkg │ ├── superpay │ └── validation ├── store │ └── postgres ├── user └── <project-name>.go
56. 56 . ├── app ├── cmd │ └── <project-name> ├── blog ├── comment ├── mock ├── pkg │ ├── superpay │ └── validation ├── store │ └── postgres ├── user └── <project-name>.go
57. pkg, internal, misc or util Whatever works for your team and you 57 . ├── app ├── cmd │ └── <project-name> ├── blog ├── comment ├── mock ├── pkg │ ├── superpay │ └── validation ├── store │ └── postgres ├── user └── <project-name>.go
58. 58 . ├── app ├── cmd │ └── <project-name> ├── blog ├── comment ├── mock ├── pkg │ ├── superpay │ └── validation ├── store │ └── postgres ├── user └── <project-name>.go
60. - util.URLError 60
61. - util.URLError - common.SanitizeMessage 61
62. - util.URLError - common.SanitizeMessage - base.EnsureAbsolutePath 62
63. - util.URLError - common.SanitizeMessage - base.EnsureAbsolutePath - helpers.IsEmail 63
64. - util.URLError - common.SanitizeMessage - base.EnsureAbsolutePath - helpers.IsEmail 64 These packages say nothing!
65. 65 - util.URLError - common.SanitizeMessage - base.EnsureAbsolutePath - helpers.IsEmail type URLError = app.URLError These packages say nothing!
66. 66 - util.URLError - common.SanitizeMessage - base.EnsureAbsolutePath - helpers.IsEmail type URLError = app.URLError var isEmail = validation.IsEmail These packages say nothing!
67. - Use multiple files - Do not separate structs and their methods (not a C/C++) - It’s okay to store few structs in one file (it’s not Java after all) - And keep test files next to code store ├── postgres │ ├── postgres.go │ ├── user.go │ └── user_test.go └── redis ├── redis.go └── comments.go 67
68. - Use multiple files - Do not separate structs and their methods (not a C/C++) - It’s okay to store few structs in one file (it’s not Java after all) - And keep test files next to code store ├── postgres │ ├── postgres.go │ ├── user.go │ └── user_test.go └── redis ├── redis.go └── comments.go // type Comment and Comment.HasImage method 68
69. - Use multiple files - Do not separate structs and their methods (not a C/C++) - It’s okay to store few structs in one file (it’s not Java after all) - And keep test files next to code store ├── postgres │ ├── postgres.go │ ├── user.go // type User and type Credentials │ └── user_test.go └── redis ├── redis.go └── comments.go 69
70. - Use multiple files - Do not separate structs and their methods (not a C/C++) - It’s okay to store few structs in one file (it’s not Java after all) - And keep test files next to code store ├── postgres │ ├── postgres.go │ ├── user.go │ └── user_test.go └── redis ├── redis.go └── comments.go 70
71. 71 postgres ├── postgres.go ├── user.go ├── stats.go └── user_test.go redis ├── redis.go ├── cache.go └── comments.go
72. 72 postgres ├── postgres.go ├── user.go ├── stats.go └── user_test.go redis ├── redis.go ├── cache.go └── comments.go cache ├── redis │ └── redis.go store ├── postgres │ ├── postgres.go │ ├── user.go │ └── user_test.go └── redis ├── redis.go └── comments.go
74. - Main packages are not importable 74
75. - Main packages are not importable - Don’t export from main, it’s useless 75
76. - Main packages are not importable - Don’t export from main, it’s useless - main package is hard to test (see above) 76
77. 77 package main func init() { config.Load() }
78. 78 package main func init() { config.Load() } func main() { os.Exit(realMain()) } func realMain() int { log.SetOutput(ioutil.Discard) // ... }
79. package main func main() { log.Fatal(app.Run()) } 79
81. - 1 init() per package (pretty please) 81
82. - 1 init() per package (pretty please) - Do not depend on init’s call order 82
83. - 1 init() per package (pretty please) - Do not depend on init’s call order - No heavy tasks 83
84. - 1 init() per package (pretty please) - Do not depend on init’s call order - No heavy tasks - Preferably no I/O, especially blocking 84
85. - 1 init() per package (pretty please) - Do not depend on init’s call order - No heavy tasks - Preferably no I/O, especially blocking - Better to not have it at all 85
86. # Python is quite flexible # try: import foo except: print(‘good try lol’) 86
87. # Python is quite flexible # try: import foo except: print(‘good try lol’) // Go isn’t so… // package foo func init() { iCanPanicAndYouCanDoNothing() } 87
88. // but wait, it can be flexible... package foo func Init() { iCanPanicButOoooohhYouCanCatchMe() } 88
89. // but wait, it can be flexible... package foo func Init() { iCanPanicButOoooohhYouCanCatchMe() } ----------- package bar func ... { defer func() { if r := recover(); r != nil { // process a panic } }() foo.Init() } 89
90. package foo func (s *Service) Process() { // let’s start a sweet goroutine go func() { iCanPanicAndYouCanDoNothing() }() } 90
91. package foo func (s *Service) Process() { // let’s start a sweet goroutine go func() { iCanPanicAndYouCanDoNothing() }() } ----------- package bar func ... { // but internal goroutine // isn’t accessible here :( s.Process() } 91
92. package foo func (s *Service) Process() { go func() { defer func() { // recovery process }() iCanPanicAndAuthorWillRecover() }() } 92
93. package foo func (s *Service) Process() { iCanPanicButItDoesntMatter() } 93
94. package foo func (s *Service) Process() { iCanPanicButItDoesntMatter() } ----------- package bar func ... { go func() { defer func() { // user defined recovery process }() s.Process() }() } 94
96. - Exported package variable is mutable by everyone 96
97. - Exported package variable is mutable by everyone - You have no power to control other packages 97
98. - Exported package variable is mutable by everyone - You have no power to control other packages - Tight coupling makes code less flexible 98
99. - Exported package variable is mutable by everyone - You have no power to control other packages - Tight coupling makes code less flexible - You cannot mock a package! 99
100. - Exported package variable is mutable by everyone - You have no power to control other packages - Tight coupling makes code less flexible - You cannot mock a package! - Logger, metrics? - mmmmaybe 100
101. - Exported package variable is mutable by everyone - You have no power to control other packages - Tight coupling makes code less flexible - You cannot mock a package! - Logger, metrics? - mmmmaybe - Config, flags? - better no 101
102. - Exported package variable is mutable by everyone - You have no power to control other packages - Tight coupling makes code less flexible - You cannot mock a package! - Logger, metrics? - mmmmaybe - Config, flags? - better no - DB driver? - NONONO 102
103. - Exported package variable is mutable by everyone - You have no power to control other packages - Tight coupling makes code less flexible - You cannot mock a package! - Logger, metrics? - mmmmaybe - Config, flags? - better no - DB driver? - NONONO 103 by the way unexported variables are also bad :(
105. - Should be simply a container for consts, types, funcs 105
106. - Should be simply a container for consts, types, funcs - Zero variables is brilliant (both exported and unexported) 106
107. - Should be simply a container for consts, types, funcs - Zero variables is brilliant (both exported and unexported) - Documentation and tests :) 107
109. - log.Printf A safe action, might be noisy, but harmless 109
110. - log.Printf A safe action, might be noisy, but harmless - log.Panicf Not idiomatic, but in an edge case might be fine 110
111. 111 - log.Printf A safe action, might be noisy, but harmless - log.Panicf Not idiomatic, but in an edge case might be fine - log.Fatalf Evil has no boundaries, omit it, no one can survive os.Exit(1) (even defer)
113. - doc.go is a README of your package 113
114. - doc.go is a README of your package - Run godoc locally to see how it looks 114
115. 115 - doc.go is a README of your package - Run godoc locally to see how it looks - Also add package documentation // Package bytes implements functions for the manipulation of byte slices. // It is analogous to the facilities of the strings package. package bytes
116. Interfaces Packages & Modules
118. Be conservative in what you send, be liberal in what you accept (с) Postel’s Law, Wikipedia 118
119. Be conservative in what you send, be liberal in what you accept (с) Postel’s Law, Wikipedia TCP architecture: 119
120. Be conservative in what you send, be liberal in what you accept (с) Postel’s Law, Wikipedia TCP architecture: - We don’t care about how packets go through network 120
121. Be conservative in what you send, be liberal in what you accept (с) Postel’s Law, Wikipedia TCP architecture: - We don’t care about how packets go through network - but we expect them in a well defined order to process 121
122. func FetchUsers(db Store) ([]*User, error) { ... } 122
123. func FetchUsers(db Store) ([]*User, error) { ... } - We don’t care what is inside: Postgres, Redis, plain file or a mock 123
124. func FetchUsers(db Store) ([]*User, error) { ... } - We don’t care what is inside: Postgres, Redis, plain file or a mock - Until it has desired API for us 124
125. func FetchUsers(db Store) ([]*User, error) { ... } - We don’t care what is inside: Postgres, Redis, plain file or a mock - Until it has desired API for us - But we know for sure that we need a specific struct User 125
126. func FetchUsers(db Store) ([]*User, error) { ... } - We don’t care what is inside: Postgres, Redis, plain file or a mock - Until it has desired API for us - But we know for sure that we need a specific struct User Tip: return error as interface, not as a struct 126
128. - There is the “Java-style” interface declaration 128
129. - There is the “Java-style” interface declaration - Define an interface 129
130. - There is the “Java-style” interface declaration - Define an interface - Create a type that implements it 130
131. 131 - There is the “Java-style” interface declaration - Define an interface - Create a type that implements it - Often you have one interface and one implementation
132. - There is the “Java-style” interface declaration - Define an interface - Create a type that implements it - Often you have one interface and one implementation That’s not a “Go style” ʕ◔ϖ◔ʔ 132
134. - Go interfaces are in the package that uses it 134
135. - Go interfaces are in the package that uses it - And this makes Go code easy to extend 135
136. Modules Packages & Modules
137. 137 time Image credit: ©Istockphoto/JamesBrey
139. - GOPATH 139
140. - GOPATH - godep 140
141. - GOPATH - godep - gopkg.in 141
142. - GOPATH - godep - gopkg.in - glide 142
143. - GOPATH - godep - gopkg.in - glide - vendor dir 143
144. - GOPATH - godep - gopkg.in - glide - vendor dir - dep 144
146. 146 - Modules - Semantic versioning - Import compatibility rule - go.mod
147. - A module is a collection of Go packages that are versioned as a single unit 147
148. - A module is a collection of Go packages that are versioned as a single unit - A module is a tree/directory of Go source files with a go.mod file in the root ├── cmd │ └── main.go ├── consum │ ├── consum.go │ └── handlers.go ├── produce │ ├── handlers.go │ ├── handlers_test.go │ └── processing.go ├── go.mod └── go.sum 148
149. - A module is a collection of Go packages that are versioned as a single unit - A module is a tree/directory of Go source files with a go.mod file in the root ├── cmd │ └── main.go ├── consum │ ├── consum.go │ └── handlers.go ├── produce │ ├── handlers.go │ ├── handlers_test.go │ └── processing.go ├── go.mod └── go.sum 149 Can leave outside of GOPATH
151. 151 - If an old and a new package have the same import path - the new package must be backwards-compatible with the old package
152. 152 - If an old and a new package have the same import path - the new package must be backwards-compatible with the old package import ( "github.com/golang/hello/hey" // v0 or v1 "github.com/golang/hello/v2/hey" )
153. 153 - auto(default) - on - off $ export GO111MODULE=on $ go build ./...
154. 154 Usage: go mod <command> [arguments] The commands are: download download modules to local cache edit edit go.mod from tools or scripts graph print module requirement graph init initialize new module in current directory tidy add missing and remove unused modules vendor make vendored copy of dependencies verify verify dependencies have expected content why explain why packages or modules are needed
155. $ mkdir /mygo/hello $ cd /mygo/hello 155
156. $ mkdir /mygo/hello $ cd /mygo/hello $ go mod init github.com/golang/hello go: creating new go.mod: module github.com/golang/hello $ ls go.mod 156
157. 157 $ mkdir /mygo/hello $ cd /mygo/hello $ go mod init github.com/golang/hello go: creating new go.mod: module github.com/golang/hello $ ls go.mod $ cat go.mod module github.com/golang/hello
158. $ git clone https://github.com/go-gitea/gitea Cloning into gitea... $ cd gitea 158
159. $ git clone https://github.com/go-gitea/gitea Cloning into gitea... $ cd gitea $ go mod init go: creating new go.mod: module github.com/go-gitea/gitea go: copying requirements from Gopkg.lock 159
160. 160 $ git clone https://github.com/go-gitea/gitea Cloning into gitea... $ cd gitea $ go mod init go: creating new go.mod: module github.com/go-gitea/gitea go: copying requirements from Gopkg.lock $ go mod tidy go: extracting github.com/PuerkitoBio/goquery v1.5.0 go: extracting github.com/blevesearch/bleve v0.7.0 go: finding github.com/google/pprof v0.0.0-20181206194817-3ea8567a2e57 go: finding golang.org/x/lint v0.0.0-20190227174305-5b3e6a55c961 go: finding golang.org/x/time v0.0.0-20181108054448-85acf8d2951c go: downloading github.com/facebookgo/grace v0.0.0-20180706040059-75cf19382434 ...
161. module github.com/hashicorp/consul go 1.12 ... 161
162. module github.com/hashicorp/consul go 1.12 require ( github.com/NYTimes/gziphandler v1.0.1 <...>/datadog-go v0.0.0-20160329135253-cc2f4770f4d6 // indirect github.com/go-redis/redis v6.15.2+incompatible ... ) 162
163. module github.com/hashicorp/consul go 1.12 require ( github.com/NYTimes/gziphandler v1.0.1 <...>/datadog-go v0.0.0-20160329135253-cc2f4770f4d6 // indirect github.com/go-redis/redis v6.15.2+incompatible ... ) 163
164. 164 module github.com/hashicorp/consul go 1.12 require ( github.com/NYTimes/gziphandler v1.0.1 <...>/datadog-go v0.0.0-20160329135253-cc2f4770f4d6 // indirect github.com/go-redis/redis v6.15.2+incompatible ... ) replace github.com/hashicorp/consul/api => ./api // can be fork or branch
165. 165 module github.com/hashicorp/consul go 1.12 require ( github.com/NYTimes/gziphandler v1.0.1 <...>/datadog-go v0.0.0-20160329135253-cc2f4770f4d6 // indirect github.com/go-redis/redis v6.15.2+incompatible ... ) replace github.com/hashicorp/consul/api => ./api // can be fork or branch exclude github.com/not-a-hacker/supergeil v1270.0.1
168. 168 cloud.google.com/go v0.26.0 h1:e0WKqKTd5BnrG8aKH3J3h+QvEIQtSUcf2n5UZ5ZgLtQ= cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw= github.com/Azure/azure-sdk-for-go v16.0.0+incompatible h1:gr1qKY/Ll72VjFTZmaBwRK1yQHAxCnV25ekOKroc9ws= github.com/Azure/azure-sdk-for-go v16.0.0+incompatible/go.mod h1:9XXNKU+eRnpl9moKnB4QOLf1HestfXbmab5FXxiDBjc= // you might want to use go mod verify
170. # same (@latest is default for 'go get') $ go get github.com/gorilla/mux@latest 170
171. # same (@latest is default for 'go get') $ go get github.com/gorilla/mux@latest # records v1.6.2 $ go get github.com/gorilla/mux@v1.6.2 $ go get github.com/gorilla/mux@e3702bed2 171
172. # same (@latest is default for 'go get') $ go get github.com/gorilla/mux@latest # records v1.6.2 $ go get github.com/gorilla/mux@v1.6.2 $ go get github.com/gorilla/mux@e3702bed2 # records v0.0.0-20180517173623-c85619274f5d $ go get github.com/gorilla/mux@c856192 172
173. 173 # same (@latest is default for 'go get') $ go get github.com/gorilla/mux@latest # records v1.6.2 $ go get github.com/gorilla/mux@v1.6.2 $ go get github.com/gorilla/mux@e3702bed2 # records v0.0.0-20180517173623-c85619274f5d $ go get github.com/gorilla/mux@c856192 # records current meaning of master $ go get github.com/gorilla/mux@master
174. # go and get a repo $ go get github.com/go-gitea/gitea $ cd ~/go/src/github.com/go-gitea/gitea 174
175. # go and get a repo $ go get github.com/go-gitea/gitea $ cd ~/go/src/github.com/go-gitea/gitea # set a env var and check why do we use this dependency $ export GO111MODULE=on $ go mod why github.com/RoaringBitmap/roaring 175
176. 176 # go and get a repo $ go get github.com/go-gitea/gitea $ cd ~/go/src/github.com/go-gitea/gitea # set a env var and check why do we use this dependency $ export GO111MODULE=on $ go mod why github.com/RoaringBitmap/roaring # github.com/RoaringBitmap/roaring code.gitea.io/gitea/modules/indexer github.com/blevesearch/bleve github.com/blevesearch/bleve/index/scorch github.com/RoaringBitmap/roaring
177. # install $ go get github.com/rogpeppe/gohack 177
178. # install $ go get github.com/rogpeppe/gohack $ gohack get example.com/foo/bar # will clone repo into $HOME/gohack/example.com/foo/bar # will add replace statement $ cat go.mod replace example.com/foo/bar => /home/rog/gohack/example.com/foo/bar 178
179. 179 # install $ go get github.com/rogpeppe/gohack $ gohack get example.com/foo/bar # will clone repo into $HOME/gohack/example.com/foo/bar # will add replace statement $ cat go.mod replace example.com/foo/bar => /home/rog/gohack/example.com/foo/bar # to remove specific replace: $ gohack undo example.com/foo/bar # to remove all replaces: $ gohack undo
181. 181 - https://proxy.golang.org - https://github.com/gomods/athens - https://github.com/goproxy/goproxy - export GOPROXY=my.proxy.com - go get github.com/foo/bar
183. *Remark Packages & Modules
185. - Usability ~ Reusability 185
186. - Usability ~ Reusability - Make application team-friendly 186
187. - Usability ~ Reusability - Make application team-friendly - Keep library easy to use 187
188. - Usability ~ Reusability - Make application team-friendly - Keep library easy to use Animated-emoji-colorful output in app - cool, whatever 188
189. - Usability ~ Reusability - Make application team-friendly - Keep library easy to use Animated-emoji-colorful output in app - cool, whatever Math library with zero allocation HTTP router - thanks, but no 189
190. Summary Packages & Modules
192. - Simple and shy packages 192
193. - Simple and shy packages - Clear naming is important 193
194. - Simple and shy packages - Clear naming is important - No global state at all 194
195. - Simple and shy packages - Clear naming is important - No global state at all - Interfaces are for abstraction 195
196. 196 - Simple and shy packages - Clear naming is important - No global state at all - Interfaces are for abstraction - Modules == Go ecosystem 2.0
197. 197 - Simple and shy packages - Clear naming is important - No global state at all - Interfaces are for abstraction - Modules == Go ecosystem 2.0 - App != Lib
198. Thank you Packages & Modules
199. - Ben Johnson @benbjohnson - Dave Cheney @davecheney - Jaana B. Dogan @rakyll - Go team ʕ◔ϖ◔ʔ - all the friends \o/ 199