使用Go你需要注意的坑在这里！

package main
import (
    "fmt"
    "time"
)
func catchError() {
    if err := recover(); err != nil {
        fmt.Println(err)
    }
}
func hole2() {
    a := 1
    if time.Now().Year() > 2020 {
        a := 2 // 一不小心加了一个冒号
        println(a)
    }
    println(a)
}
func hole3() {
    defer catchError()
    var m0 map[string]string
    println("key:", m0["key"])
    m0["key"] = "val" // 报错：assignment to entry in nil map
}
type Hole4 struct {
    Name    string
    Slices  []string
    MyMap   map[string]string
    Channel chan int
}
func hole4() {
    a := Hole4{
        Name:    "a",
        Slices:  []string{"a"},
        MyMap:   map[string]string{"key": "a"},
        Channel: make(chan int),
    }
    go func() {
        for n := range a.Channel {
            fmt.Println(n)
        }
    }()
    b := a
    b.Name = "b"
    b.Slices[0] = "b"
    b.MyMap["key"] = "b"
    b.Channel <- 999
    fmt.Println(a)
    fmt.Println(b)
}
func hole5() {
    slice1 := make([]string, 1, 1)
    slice1[0] = "1"
    temp1 := slice1
    temp1 = append(temp1, "1")
    temp1[0] = "2"
    fmt.Println(slice1)
    slice9 := make([]string, 1, 9)
    slice9[0] = "1"
    temp2 := slice9
    temp2 = append(temp2, "1")
    temp2[0] = "2"
    fmt.Println(slice9)
}
type Cache interface {
    Name()
}
type RedisCache struct{}
func (RedisCache) Name() {}
func hole6() {
    defer catchError()
    var redis1 *RedisCache = nil
    var redis2 Cache = redis1
    if redis2 != nil {
        println("entering...")
        redis2.Name() // 报错：nil pointer dereference
    }
}
func main() {
    hole2()
    hole3()
    hole4()
    hole5()
    hole6()
}