go并发访问map的坑 fatal error: concurrent map read and map write

package main
import "fmt"
func test() map[string]interface{}{
  taskList := []string{"a", "b"}
  result := make(map[string]interface{})
  for _, task := range taskList {
    go func(task string) {
      switch task {
      case "a":
        result["a"] = "xiaofei"
      case "b":
        result["b"] = "ceshi"
      }
    }(task)
  }
  return result
}
func main() {
  for a := 0; a < 1000; a++ {
    fmt.Println(test())
  }
}

package main
import (
  "fmt"
  "sync"
)
// 使用读写锁 sync.RWMutex
type NewMap struct {
  lock *sync.RWMutex
  sm   map[interface{}]interface{}
}
func (m *NewMap) Set(k interface{}, v interface{}) bool {
  m.lock.Lock()
  defer m.lock.Unlock()
  m.sm[k] = v
  return true
}
func test() map[interface{}]interface{} {
  taskList := []string{"a", "b"}
  xf := &sync.WaitGroup{}
  result := NewMap{
    lock: new(sync.RWMutex),
    sm: make(map[interface{}]interface{}),
  }
  for _, task := range taskList {
    xf.Add(1)
    go func(task string) {
      defer xf.Done()
      switch task {
      case "a":
        result.Set("a", "xiaofei")
      case "b":
        result.Set("b", "ceshi")
      }
    }(task)
  }
  xf.Wait()
  return result.sm
}
func main() {
  for a := 0; a < 100; a++ {
    fmt.Println(test())
  }
}