go - Redigo:尝试连接到池时无效的内存地址或零指针取消引用

Question

Redis Connecting.....! panic: runtime error: invalid memory address or
nil pointer dereference [signal 0xb code=0x1 addr=0x28 pc=0x40154b]
goroutine 1 [running]: runtime.panic(0x52c6e0, 0x6b6348)
/usr/lib/go/src/pkg/runtime/panic.c:266 +0xb6
main.func·001(0xc21005102c, 0x0, 0x4bcd4c, 0x1)
/home/vinay10949/redischeck/redischeck.go:21 +0x10b
github.com/garyburd/redigo/redis.(*Pool).get(0xc210051000, 0x0,
0xc2100378f0, 0x42dbdf, 0x7fbe9c177070) /usr/lib/go/src/pkg/github.com/garyburd/redigo/redis/pool.go:250
+0x3a2 github.com/garyburd/redigo/redis.(*Pool).Get(0xc210051000, 0x1, 0x1) > /usr/lib/go/src/pkg/github.com/garyburd/redigo/redis/pool.go:150
+0x27 main.main() /home/

vinay10949/redischeck/redischeck.go:29 +0x13e

package main

import (
    "flag"
    "fmt"
    "github.com/garyburd/redigo/redis"
    //"reflect"
)

var (
    redisAddress   = flag.String("10.12.2.121", "10.12.2.121:6379", "Address to the Redis server")
    maxConnections = flag.Int("max-connections", 10, "Max connections to Redis")
)

func main() {

    //Redis Connection
    redisPool := redis.NewPool(func() (redis.Conn, error) {

        con, err := redis.Dial("tcp", *redisAddress)
        con.Do("SELECT", 1)
        if err != nil {
            return nil, err
        }
        return con, err
    }, *maxConnections)

    fmt.Println("Redis Connecting...!")
    con := redisPool.Get()
    status, errStatus := con.Do("SET", "Name", "BookMyShow")
    if errStatus != nil {
        fmt.Println(errStatus)
    } else {
        fmt.Println("Redis Connected")
    }
    statusInsertion, _ := redis.String(status, errStatus)
    fmt.Println("Status of Insertion :" + statusInsertion)
    value, _ := redis.String(con.Do("GET", "Name"))
    fmt.Println("Value Retrieved : " + value)
}

Answer 1

您在使用返回值之后检查错误是错误的:

con, err := redis.Dial("tcp", *redisAddress)
con.Do("SELECT", 1) // Here you are using con which most likely is nil
if err != nil {
    return nil, err
}

将代码重新排列为:

con, err := redis.Dial("tcp", *redisAddress)
if err != nil {
    return nil, err
}
con.Do("SELECT", 1) // con should be used after checking for errors