:= len(b) - i - 1 b[i], b[j] = b[j], b[i] } return string(b) } YouTube 3 ~/gocode/src/github.com/nf/string$ go build ~/gocode/src/github.com/nf/string$ go install ~/gocode/src/github.com/nf/string$ ls ~/gocode/pkg/darwin_amd64/github.com/nf string.a ~/gocode/src/github.com/nf/string$ cd ../hello ~/gocode/src/github.com/nf/hello$ vim hello.go hello.go package main import ( "fmt" "github.com/nf/string" ) func main() { fmt.Println(string.Reverse("Hello, new gopher!")) } YouTube 4 ~/gocode/src/github.com/nf/hello$ go install ~/gocode/src/github.com/nf/hello$ hello !rehpog wen ,olleH ~/gocode/src/github.com/nf/hello$ cd ../string ~/gocode/src/github.com/nf/string$ vim string_test.go string_test.go package string import "testing" func Test(t *testing.T) { var tests = []struct { s, want string }{ {"Backward", "drawkcaB"}, {"Hello, 世界", "界世 ,olleH"}, {"", ""}, }