First time using Golang

package main

import "fmt"

func main() {
  fmt.Println("Hello World!")
}

// Concurrency
package main

import (
  "fmt"
  "time"
)

func readword(ch chan string) {
  fmt.Println("Type a word, then hit Enter.")
  var word string
  fmt.Scanf("%s", &word)
  ch <- word
}

func timeout(t chan bool) {
  time.Sleep(5 * time.Second)
  t <- false
}

func main() {
  t := make(chan bool)
  go timeout(t)
  
  ch := make(chan string)
  go readword(ch)
  
  select {
  case word := <-ch:
    fmt.Println("Received", word)
  case <-t:
    fmt.Println("Timeout.")
  }
}

// testing
func ExtractUsername(email string) string {
  at := strings.Index(email, "@")
  return email[:at]
}

//----

import (
  "testing"
)

func TestExtractUsername(t *testing.T) {
  t.Run("withoutDot", func(t *testing.T) {
    username := ExtractUsername("r@google.com")
    if username != "r" {
      t.Fatalf("Got: %v\n", username)
    }
  })
  
  t.Run("withDot", func(t *testing.T) {
    username := ExtractUsername("john.smith@example.com")
    if username != "john.smith" {
      t.Fatalf("Got: %v\n", username)
    }
  })
}

// web app
package main

import (
  "fmt"
  "log"
  "net/http"
)

func helloFunc(w http.ResponseWriter, r *http.Request) {
  fmt.Fprintf(w, "Hello World!")
}

func main() {
  http.HandleFunc("/", helloFunc)
  log.Fatal(http.ListenAndServe(":8080", nil))
}

// packages.go
package main

import (
    "fmt"
    "math/rand"
)

func main() {
    fmt.Println("My favorite number is", rand.Intn(10))
}

// imports.go
package main

import (
    "fmt"
    "math"
)

func main() {
    fmt.Println("Now you have %g problems.\n", math.Sqrt(7))
}

// exported-names.go
package main

import (
    "fmt"
    "math"
)

func main() {
    fmt.Println(math.Pi)
}

// functions.go
package main

import "fmt"

func add(x, y int) int {
    return x + y
}

func main() {
    fmt.Println(add(42, 13))
}

// multiple-results.go
package main

import "fmt"

func swap(x, y, z string) (string, string, string) {
    return y, x, z
}

func main() {
    a, b, c := swap("Hello", "World", "!")
    fmt.Println(a,b,c)