Introduction to Go (golang)

Presentation given at DA-IICT, Gandhinagar

Transcript

1. Introduction to Go (golang) 04 Nov 2015 Niket Patel Director, Beehively
2. What is Go? G o i s a n o p e n s o u r c e p r o g r a m m i n g l a n g u a g e t h a t m a k e s i t e a s y t o b u i l d s i m p l e , r e l i a b l e , a n d e f f i c i e n t s o f t w a r e . - h t t p : / / g o l a n g . o r g
3. Hello, World p a c k a g e m a i n f u n c m a i n ( ) { p r i n t ( " H e l l o , अहमदाबाद . " ) } Run
4. Features of Go Concurrency GC Interfaces Composition (over inheritance) Orthogonal Fast compilation Cross compilation Static Binary NO classical OOP
5. Projects built using Go Docker dl.google.com (downloads from google) vitess.io (mysql proxy developed by youtube) CoreOS Google kubernetes InfluxDB https://github.com/golang/go/wiki/Projects
6. Companies using Go Beehively Google Dropbox Heroku Github Twitter Canonical (Ubuntu) Cloudflare bit.ly ThoughtWorks Qwinix More... (https://github.com/golang/go/wiki/GoUsers)
7. Introduction to Go Syntax
8. Packages, Imports ValueOfPi function is exported and visible outside package. calculatedPi function is visible only inside package. p a c k a g e m a i n i m p o r t " f m t " i m p o r t " m a t h " c o n s t L i m i t = 1 0 0 0 0 0 0 0 0 v a r l i m i t = 1 0 0 0 0 0 0 0 0 f u n c m a i n ( ) { f m t . P r i n t l n ( " P I : \ n C a l c u l a t e d " , V a l u e O f P i ( ) , " \ n C o n s t a n t " , m a t h . P i ) } f u n c V a l u e O f P i ( ) f l o a t 6 4 { r e t u r n c a l c u l a t e d P i ( L i m i t ) } f u n c c a l c u l a t e d P i ( l i m i t f l o a t 6 4 ) f l o a t 6 4 { Run
9. Variables f u n c c a l c u l a t e d P i ( l i m i t f l o a t 6 4 ) f l o a t 6 4 { v a r s u m f l o a t 6 4 v a r n u m , t o g g l e = 4 . 0 , t r u e f o r i : = 1 . 0 ; i < l i m i t ; i + = 2 { i f t o g g l e { s u m + = n u m / i } e l s e { s u m - = n u m / i } t o g g l e = ! t o g g l e } r e t u r n s u m } Run
10. Conditions p a c k a g e m a i n i m p o r t " f m t " v a r a g e L i m i t = 6 0 f u n c m a i n ( ) { v a r a g e = 3 6 i f o v e r l i m i t ( a g e ) { f m t . P r i n t l n ( a g e , " i s o v e r l i m i t " ) } e l s e { f m t . P r i n t l n ( a g e , " i s u n d e r l i m i t " ) } } f u n c o v e r l i m i t ( a g e i n t ) b o o l { r e t u r n a g e > a g e L i m i t } Run
11. Loops f u n c m a i n ( ) { v a r l o o p b o o l v a r i t e m s = [ ] s t r i n g { " O n e " , " T w o " , " T h r e e " } f o r i , i t e m : = r a n g e i t e m s { f m t . P r i n t l n ( i , i t e m ) } f o r i : = 0 ; i < l e n ( i t e m s ) ; i + + { f m t . P r i n t l n ( i , i t e m s [ i ] ) } f o r l o o p { f m t . P r i n t l n ( " N e v e r r e a c h e d " ) } f o r { / / i n f i n i t e l o o p } } Run
12. Functions f u n c m a i n ( ) { f m t . P r i n t l n ( g e t A g e ( ) ) f m t . P r i n t l n ( g e t N a m e A n d A g e ( ) ) f m t . P r i n t l n ( b e t t e r N a m e A n d A g e ( ) ) } f u n c g e t A g e ( ) i n t { r e t u r n 3 3 } f u n c g e t N a m e A n d A g e ( ) ( n a m e s t r i n g , a g e i n t ) { n a m e = " J o h n " a g e = g e t A g e ( ) r e t u r n } f u n c b e t t e r N a m e A n d A g e ( ) ( s t r i n g , i n t ) { n a m e : = " J o h n " r e t u r n n a m e , g e t A g e ( ) } Run
13. Structs t y p e A g e s t r u c t { t i m e . D u r a t i o n } t y p e P e r s o n s t r u c t { f i r s t N a m e , l a s t N a m e s t r i n g o c c u p a t i o n s t r i n g a g e A g e } f u n c m a i n ( ) { p e r s o n : = P e r s o n { } p e r s o n . f i r s t N a m e = " V i j a y " p e r s o n . l a s t N a m e = " D e e n a n a t h C h a u h a n " p e r s o n . a g e = A g e { 3 6 * 3 6 5 * 2 4 * t i m e . H o u r } f m t . P r i n t l n ( p e r s o n . f i r s t N a m e , p e r s o n . l a s t N a m e , " i s " , p e r s o n . a g e , " o l d . " ) } Run
14. Methods f u n c ( t P e r s o n ) S a y N a m e ( ) s t r i n g { r e t u r n f m t . S p r i n t f ( " M y N a m e i s % s \ n . . . % s % s " , t . l a s t N a m e , t . f i r s t N a m e , t . l a s t N a m e , ) } f u n c m a i n ( ) { p e r s o n : = P e r s o n { } p e r s o n . f i r s t N a m e = " J a m e s " p e r s o n . l a s t N a m e = " B o n d " f m t . P r i n t l n ( p e r s o n . S a y N a m e ( ) ) } Run
15. Methods f u n c ( t A g e n t ) S t r i n g ( ) s t r i n g { r e t u r n f m t . S p r i n t f ( " M y N a m e i s % s \ n . . . % s % s " , t . l a s t N a m e , t . f i r s t N a m e , t . l a s t N a m e , ) } f u n c m a i n ( ) { a g e n t : = A g e n t { } a g e n t . f i r s t N a m e = " J a m e s " a g e n t . l a s t N a m e = " B o n d " f m t . P r i n t l n ( a g e n t ) } Run
16. Zero Value p a c k a g e m a i n i m p o r t " f m t " t y p e A s t r u c t { n a m e s t r i n g a g e f l o a t 6 4 } f u n c m a i n ( ) { v a r s t r s t r i n g v a r n u m i n t 6 4 v a r a A f m t . P r i n t f ( " % # v , \ n % # v , \ n % # v \ n " , s t r , n u m , a ) } Run
17. Interfaces t y p e M a s s i n t t y p e W o o d s t r u c t { M a s s } t y p e P a p e r s t r u c t { M a s s } t y p e B u r n e r i n t e r f a c e { C a n B u r n ( ) b o o l B u r n T i m e ( ) M a s s }
18. Interfaces (cont'd...) f u n c ( m M a s s ) C a n B u r n ( ) b o o l { r e t u r n m > 0 } f u n c ( w W o o d ) B u r n T i m e ( ) M a s s { r e t u r n 1 0 * w . M a s s } f u n c ( p P a p e r ) B u r n T i m e ( ) M a s s { r e t u r n 1 * p . M a s s } f u n c B u r n ( b B u r n e r ) { i f b . C a n B u r n ( ) { f m t . P r i n t f ( " % T w i l l b u r n f o r % d s e c o n d s \ n " , b , b . B u r n T i m e ( ) ) } e l s e { f m t . P r i n t f ( " % T c a n ' t b u r n \ n " , b ) } } f u n c m a i n ( ) { B u r n ( W o o d { 1 0 } ) B u r n ( P a p e r { 1 0 } ) B u r n ( P a p e r { 0 } ) } / / Run
19. Pointers p a c k a g e m a i n i m p o r t " f m t " f u n c m a i n ( ) { v a r a i n t a = 3 f m t . P r i n t l n ( a , & a ) f m t . P r i n t f ( " % T % T \ n " , a , & a ) v a r b i n t v a r p * i n t f m t . P r i n t l n ( b , p ) p = & b f m t . P r i n t l n ( b , p ) } Run
20. Pointers (cont'd...) p a c k a g e m a i n i m p o r t " f m t " t y p e P e r s o n s t r u c t { n a m e s t r i n g } f u n c m a i n ( ) { a : = P e r s o n { " A " } f m t . P r i n t l n ( a . n a m e ) a . c h a n g e N a m e ( ) f m t . P r i n t ( a . n a m e ) } f u n c ( p P e r s o n ) c h a n g e N a m e ( ) { p . n a m e = " B " } Run
21. Slices p a c k a g e m a i n i m p o r t " f m t " f u n c m a i n ( ) { v a r a [ ] s t r i n g a = a p p e n d ( a , " V i j a y " ) f m t . P r i n t l n ( a ) v a r b = [ ] s t r i n g { " 1 " , " 2 " , " 3 " , " 4 " , " 5 " } f m t . P r i n t l n ( b ) } Run
22. Slices p a c k a g e m a i n i m p o r t " f m t " f u n c m a i n ( ) { v a r a = [ 3 ] s t r i n g { " 1 " , " V i j a y " , " 3 " } v a r b = a [ 0 : 3 ] / / c r e a t e s l i c e f r o m a r r a y f m t . P r i n t l n ( b ) b = a p p e n d ( b , " 4 " ) b = a p p e n d ( b , " 5 " ) f m t . P r i n t l n ( b ) } Run
23. Maps p a c k a g e m a i n i m p o r t " f m t " f u n c m a i n ( ) { v a r m m a p [ s t r i n g ] f l o a t 6 4 m [ " v a l u e O f Z e r o " ] = 0 . 0 f m t . P r i n t l n ( m [ " v a l u e O f Z e r o " ] ) } Run
24. Maps p a c k a g e m a i n i m p o r t " f m t " t y p e W e e k d a y i n t v a r d a y s = m a k e ( m a p [ i n t ] s t r i n g ) f u n c i n i t ( ) { d a y s [ 0 ] = " S u n d a y " d a y s [ 1 ] = " M o n d a y " d a y s [ 2 ] = " T u e s d a y " } f u n c m a i n ( ) { v a r d W e e k d a y f m t . P r i n t l n ( d ) } f u n c ( d W e e k d a y ) S t r i n g ( ) s t r i n g { r e t u r n d a y s [ i n t ( d ) ] } Run
25. Error handling p a c k a g e m a i n i m p o r t ( " i o " " o s " ) f u n c m a i n ( ) { f i l e , e r r : = o s . O p e n ( " e r r 2 . g o " ) d i e ( e r r ) i o . C o p y ( o s . S t d o u t , f i l e ) } f u n c d i e ( e r r e r r o r ) { i f e r r ! = n i l { p a n i c ( e r r ) } } Run
26. Error handling (Cont'd...) p a c k a g e m a i n i m p o r t ( " i o " " l o g " " o s " ) f u n c m a i n ( ) { f i l e , e r r : = o s . O p e n ( " e r r . g o " ) i f e r r ! = n i l { l o g . P r i n t l n ( e r r ) } i f _ , e r r : = i o . C o p y ( o s . S t d o u t , f i l e ) ; e r r ! = n i l { l o g . P r i n t l n ( e r r ) } } Run
27. Embedding t y p e R e a d e r i n t e r f a c e { R e a d ( p [ ] b y t e ) ( n i n t , e r r e r r o r ) } t y p e W r i t e r i n t e r f a c e { W r i t e ( p [ ] b y t e ) ( n i n t , e r r e r r o r ) } t y p e R e a d e r W r i t e r i n t e r f a c e { R e a d e r W r i t e r }
28. Embedding (cont'd...) t y p e P e r s o n s t r u c t { f i r s t N a m e , l a s t N a m e s t r i n g } t y p e T e a c h e r s t r u c t { P e r s o n S u b j e c t s t r i n g } f u n c m a i n ( ) { t : = T e a c h e r { } t . f i r s t N a m e = " J o h n " t . l a s t N a m e = " D o e " t . S u b j e c t = " E n g l i s h " f m t . P r i n t l n ( t ) } f u n c ( t T e a c h e r ) S t r i n g ( ) s t r i n g { r e t u r n f m t . S p r i n t f ( " % s % s ( % s ) " , t . f i r s t N a m e , t . l a s t N a m e , t . S u b j e c t ) } Run
29. Concurrency
30. Concurrency is not Parallelism Concurrency is when two tasks can start, run, and complete in overlapping time periods. It doesn't necessarily mean they'll ever both be running at the same instant. Parallelism is when tasks literally run at the same time.
31. Concurrency Primitives in Go Goroutines ("go" keyword) select channel types channel operators
32. Concurrency Primitives in Go f u n c m a i n ( ) { f o r n u m : = 0 ; n u m < 2 0 ; n u m + + { j o b ( n u m ) } } f u n c j o b ( n u m i n t ) { t i m e . S l e e p ( t i m e . D u r a t i o n ( n u m * 1 2 0 ) * t i m e . M i l l i s e c o n d ) f m t . P r i n t l n ( " J o b " , n u m ) } Run
33. Concurrency Primitives in Go f u n c m a i n ( ) { f o r n u m : = 0 ; n u m < 2 0 ; n u m + + { g o j o b ( n u m ) } t i m e . S l e e p ( 5 * t i m e . S e c o n d ) } f u n c j o b ( n u m i n t ) { t i m e . S l e e p ( t i m e . D u r a t i o n ( n u m * 1 2 0 ) * t i m e . M i l l i s e c o n d ) f m t . P r i n t l n ( " J o b " , n u m ) } Run
34. Concurrency Primitives in Go f u n c m a i n ( ) { v a r w g s y n c . W a i t G r o u p f o r n u m : = 0 ; n u m < 2 0 ; n u m + + { w g . A d d ( 1 ) g o j o b ( n u m , & w g ) } w g . W a i t ( ) } f u n c j o b ( n u m i n t , w g * s y n c . W a i t G r o u p ) { t i m e . S l e e p ( t i m e . D u r a t i o n ( n u m * 1 2 0 ) * t i m e . M i l l i s e c o n d ) f m t . P r i n t l n ( " J o b " , n u m ) w g . D o n e ( ) } Run
35. Concurrency Primitives in Go f u n c m a i n ( ) { c o u n t , t 1 : = 1 0 , t i m e . N o w ( ) v a r r e s u l t = m a k e ( c h a n i n t ) f o r i : = 0 ; i < c o u n t ; i + + { g o j o b ( r e s u l t ) } f o r i : = 0 ; i < c o u n t ; i + + { f m t . P r i n t l n ( " J o b " , i , " " , < - r e s u l t ) } f m t . P r i n t l n ( " T o o k " , t i m e . N o w ( ) . S u b ( t 1 ) ) } f u n c j o b ( r e s u l t c h a n i n t ) { r e s u l t < - d o J o b ( ) } Run
36. Concurrency Primitives in Go f u n c m a i n ( ) { c o u n t , t 1 : = 1 0 , t i m e . N o w ( ) d e f e r f u n c ( ) { f m t . P r i n t l n ( " T o o k " , t i m e . N o w ( ) . S u b ( t 1 ) ) } ( ) v a r r e s u l t = m a k e ( c h a n i n t ) f o r i : = 0 ; i < c o u n t ; i + + { g o j o b ( r e s u l t ) } t i m e o u t : = t i m e . N e w T i m e r ( 2 * t i m e . S e c o n d ) f o r i : = 0 ; i < c o u n t ; i + + { s e l e c t { c a s e r e s : = < - r e s u l t : f m t . P r i n t l n ( " J o b " , i , " " , r e s ) c a s e < - t i m e o u t . C : r e t u r n } } } Run
37. Resources How to write Go code (https://www.youtube.com/watch?v=XCsL89YtqCs) How I start (https://howistart.org/posts/go/1) Go Tour (https://tour.golang.org/welcome/1) Effective Go (https://golang.org/doc/effective_go.html)
38. Thank you 04 Nov 2015 Tags: meetup, golang, introduction (#ZgotmplZ) Niket Patel Director, Beehively niket@beehively.com (mailto:niket@beehively.com) @nexneo (http://twitter.com/nexneo)