Generating random numbers over a range in Go

All the integer functions in math/rand generate non-negative numbers.

rand.Int() int              // [0, MaxInt]
rand.Int31() int32          // [0, MaxInt32]
rand.Int31n(n int32) int32  // [0, n)
rand.Int63() int64          // [0, MaxInt64]
rand.Int63n(n int64) int64  // [0, n)
rand.Intn(n int) int        // [0, n)

I would like to generate random numbers in the range [-m, n). In other words, I would like to generate a mix of positive and negative numbers.

I found this example at Go Cookbook, which is equivalent to rand.Range(min, max int) (if that function existed):

rand.Intn(max - min) + min

Don't forget to seed the PRNG before calling any rand function.

rand.Seed(time.Now().UnixNano())

This will generate random numbers within given range [a, b]

rand.Seed(time.Now().UnixNano())
n := a + rand.Intn(b-a+1)

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