1package main
2
3import "fmt"
4
5func main() {
6  fmt.Println("Hello World!")
7}

 1// Concurrency
 2package main
 3
 4import (
 5  "fmt"
 6  "time"
 7)
 8
 9func readword(ch chan string) {
10  fmt.Println("Type a word, then hit Enter.")
11  var word string
12  fmt.Scanf("%s", &word)
13  ch <- word
14}
15
16func timeout(t chan bool) {
17  time.Sleep(5 * time.Second)
18  t <- false
19}
20
21func main() {
22  t := make(chan bool)
23  go timeout(t)
24  
25  ch := make(chan string)
26  go readword(ch)
27  
28  select {
29  case word := <-ch:
30    fmt.Println("Received", word)
31  case <-t:
32    fmt.Println("Timeout.")
33  }
34}

 1// testing
 2func ExtractUsername(email string) string {
 3  at := strings.Index(email, "@")
 4  return email[:at]
 5}
 6
 7//----
 8
 9import (
10  "testing"
11)
12
13func TestExtractUsername(t *testing.T) {
14  t.Run("withoutDot", func(t *testing.T) {
15    username := ExtractUsername("r@google.com")
16    if username != "r" {
17      t.Fatalf("Got: %v\n", username)
18    }
19  })
20  
21  t.Run("withDot", func(t *testing.T) {
22    username := ExtractUsername("john.smith@example.com")
23    if username != "john.smith" {
24      t.Fatalf("Got: %v\n", username)
25    }
26  })
27}

 1// web app
 2package main
 3
 4import (
 5  "fmt"
 6  "log"
 7  "net/http"
 8)
 9
10func helloFunc(w http.ResponseWriter, r *http.Request) {
11  fmt.Fprintf(w, "Hello World!")
12}
13
14func main() {
15  http.HandleFunc("/", helloFunc)
16  log.Fatal(http.ListenAndServe(":8080", nil))
17}

 1// packages.go
 2package main
 3
 4import (
 5    "fmt"
 6    "math/rand"
 7)
 8
 9func main() {
10    fmt.Println("My favorite number is", rand.Intn(10))
11}

 1// imports.go
 2package main
 3
 4import (
 5    "fmt"
 6    "math"
 7)
 8
 9func main() {
10    fmt.Println("Now you have %g problems.\n", math.Sqrt(7))
11}

 1// exported-names.go
 2package main
 3
 4import (
 5    "fmt"
 6    "math"
 7)
 8
 9func main() {
10    fmt.Println(math.Pi)
11}

 1// functions.go
 2package main
 3
 4import "fmt"
 5
 6func add(x, y int) int {
 7    return x + y
 8}
 9
10func main() {
11    fmt.Println(add(42, 13))
12}

 1// multiple-results.go
 2package main
 3
 4import "fmt"
 5
 6func swap(x, y, z string) (string, string, string) {
 7    return y, x, z
 8}
 9
10func main() {
11    a, b, c := swap("Hello", "World", "!")
12    fmt.Println(a,b,c)