How Come In Golang Once You Seed Rand Stays Seeded

Go Programming

When I first started working with Go, I encountered an interesting aspect of the rand package – the fact that once you seed the random number generator, it stays seeded. This behavior puzzled me at first, but after digging deep into the Go documentation and experimenting with the rand package, I gained a better understanding of this unique feature.

Understanding the seed in Go’s rand package

The seed in the rand package is used to initialize the default Source to a deterministic state. When we seed the random number generator using rand.Seed(seed), Go sets the default Source to a new random number generator and initializes it with the provided seed. This means that subsequent calls to functions like rand.Intn() or rand.Float64() will produce the same sequence of pseudo-random numbers.

Personal Experimentation

Initially, I found this behavior somewhat counterintuitive. Coming from other programming languages, I was used to the idea that every time I needed a random number, I could simply call a function and get a newly generated random value without having to explicitly manage the seed.

However, after working on a few projects where reproducible randomness was crucial, I discovered the true power of this design. By explicitly seeding the random number generator, I was able to create predictable and reproducible results, which is incredibly valuable in testing and simulations.

The Implications

The fact that the seed stays seeded in Go’s rand package brings both benefits and potential pitfalls. On the positive side, it allows for deterministic behavior, ensuring that a given seed will always produce the same sequence of random numbers. This can be extremely useful in applications where reproducibility is paramount, such as scientific simulations or game development.

However, it’s important to be mindful of the implications of a seeded random number generator. In situations where true randomness is necessary, such as cryptographic applications, relying on the default seeded behavior of the rand package can lead to security vulnerabilities. In such cases, it’s crucial to use a cryptographically secure random number generator instead of the default pseudo-random number generator provided by the rand package.


In conclusion, the behavior of the seed in Go’s rand package is a deliberate design choice that offers both advantages and potential pitfalls. By understanding and harnessing this behavior, developers can create reproducible randomness when needed, while also being mindful of its limitations in scenarios where true randomness is required. This unique feature of the rand package adds a layer of control and predictability to random number generation in Go, ultimately contributing to the language’s versatility and flexibility.