crash with 'concurrent map read and map write' error

[shuxiao9058]

fatal error: concurrent map read and map write

goroutine 264720 [running]:
runtime.throw(0x79cf89, 0x21)
        /usr/local/golang/go/src/runtime/panic.go:608 +0x72 fp=0xc0006ed770 sp=0xc0006ed740 pc=0x42c262
runtime.mapaccess2(0x72b9c0, 0xc0002b59e0, 0xc000ac4b30, 0x7f9d80, 0x496b00)
        /usr/local/golang/go/src/runtime/map.go:453 +0x223 fp=0xc0006ed7b8 sp=0xc0006ed770 pc=0x40ed83
reflect.mapaccess(0x72b9c0, 0xc0002b59e0, 0xc000ac4b30, 0x7980da)
        /usr/local/golang/go/src/runtime/map.go:1249 +0x3f fp=0xc0006ed7f0 sp=0xc0006ed7b8 pc=0x410d4f
reflect.Value.MapIndex(0x72b9c0, 0xc0002b59e0, 0x15, 0x719f60, 0xc000ac4b30, 0x98, 0x72a2e0, 0xc0003f86e0, 0x94)
        /usr/local/golang/go/src/reflect/value.go:1111 +0x11d fp=0xc0006ed870 sp=0xc0006ed7f0 pc=0x4b221d
encoding/json.(*mapEncoder).encode(0xc00026c140, 0xc0009e0160, 0x72b9c0, 0xc0002b59e0, 0x15, 0x720100)
        /usr/local/golang/go/src/encoding/json/encode.go:692 +0x329 fp=0xc0006ed9e0 sp=0xc0006ed870 pc=0x652159
encoding/json.(*mapEncoder).encode-fm(0xc0009e0160, 0x72b9c0, 0xc0002b59e0, 0x15, 0xc0002b0100)
        /usr/local/golang/go/src/encoding/json/encode.go:708 +0x64 fp=0xc0006eda20 sp=0xc0006ed9e0 pc=0x65a6c4
encoding/json.(*encodeState).reflectValue(0xc0009e0160, 0x72b9c0, 0xc0002b59e0, 0x15, 0xc0002b0100)
        /usr/local/golang/go/src/encoding/json/encode.go:333 +0x82 fp=0xc0006eda58 sp=0xc0006eda20 pc=0x64f3f2
encoding/json.interfaceEncoder(0xc0009e0160, 0x72a2e0, 0xc000011210, 0x194, 0xc000010100)
        /usr/local/golang/go/src/encoding/json/encode.go:619 +0xab fp=0xc0006edaa0 sp=0xc0006eda58 pc=0x65164b
encoding/json.(*ptrEncoder).encode(0xc00026c0e8, 0xc0009e0160, 0x70b200, 0xc000011210, 0x16, 0x700100)
        /usr/local/golang/go/src/encoding/json/encode.go:788 +0xb3 fp=0xc0006edae8 sp=0xc0006edaa0 pc=0x6530d3
encoding/json.(*ptrEncoder).encode-fm(0xc0009e0160, 0x70b200, 0xc000011210, 0x16, 0xc000770100)
        /usr/local/golang/go/src/encoding/json/encode.go:793 +0x64 fp=0xc0006edb28 sp=0xc0006edae8 pc=0x65a844
encoding/json.(*encodeState).reflectValue(0xc0009e0160, 0x70b200, 0xc000011210, 0x16, 0xa10100)
        /usr/local/golang/go/src/encoding/json/encode.go:333 +0x82 fp=0xc0006edb60 sp=0xc0006edb28 pc=0x64f3f2
encoding/json.(*encodeState).marshal(0xc0009e0160, 0x70b200, 0xc000011210, 0x100, 0x0, 0x0)
        /usr/local/golang/go/src/encoding/json/encode.go:305 +0xf4 fp=0xc0006edba8 sp=0xc0006edb60 pc=0x64eea4
encoding/json.Marshal(0x70b200, 0xc000011210, 0xc000941470, 0x445787, 0x0, 0xc000941488, 0x3)
        /usr/local/golang/go/src/encoding/json/encode.go:160 +0x52 fp=0xc0006edc20 sp=0xc0006edba8 pc=0x64e942
github.com/bitly/go-simplejson.(*Json).MarshalJSON(0xc000011210, 0xc0009414d8, 0x507afd, 0x0, 0xc00081c847, 0xf)
        /usr/local/golang/gopath/src/github.com/bitly/go-simplejson/simplejson.go:53 +0x39 fp=0xc0006edc68 sp=0xc0006edc20 pc=0x65b549
github.com/bitly/go-simplejson.(*Json).Encode(0xc000011210, 0x4, 0x0, 0xf, 0xf, 0xc00081c847)
        /usr/local/golang/gopath/src/github.com/bitly/go-simplejson/simplejson.go:43 +0x2b fp=0xc0006edca8 sp=0xc0006edc68 pc=0x65b4cb

[ljluestc]

import (
    "sync"
)

// Define a struct that includes the map and a mutex.
type MapWithMutex struct {
    m   map[string]int
    mu  sync.Mutex
}

func main() {
    // Create an instance of MapWithMutex.
    mwm := MapWithMutex{
        m: make(map[string]int),
    }

    // Create and start multiple goroutines.
    for i := 0; i < 10; i++ {
        go func(i int) {
            key := strconv.Itoa(i)

            // Lock the mutex before accessing the map.
            mwm.mu.Lock()
            defer mwm.mu.Unlock()

            // Perform read or write operations on the map.
            mwm.m[key] = i
            value := mwm.m[key]
            fmt.Printf("Goroutine %d: Key %s, Value %d\n", i, key, value)
        }(i)
    }

    // Wait for the goroutines to finish.
    time.Sleep(time.Second)
}