Generating random number in Go Sun, May 24, 2020

https://github.com/grpc/grpc-go/blob/master/internal/grpcrand/grpcrand.go

package grpcrand

import (
    "math/rand"
    "sync"
    "time"
)

var (
    r  = rand.New(rand.NewSource(time.Now().UnixNano()))
    mu sync.Mutex
)

// Int63n implements rand.Int63n on the grpcrand global source.
func Int63n(n int64) int64 {
    mu.Lock()
    res := r.Int63n(n)
    mu.Unlock()
    return res
}

// Intn implements rand.Intn on the grpcrand global source.
func Intn(n int) int {
    mu.Lock()
    res := r.Intn(n)
    mu.Unlock()
    return res
}

// Float64 implements rand.Float64 on the grpcrand global source.
func Float64() float64 {
    mu.Lock()
    res := r.Float64()
    mu.Unlock()
    return res
}