One of the things to consider when comparing C# and Go is how it does parallelism. In C#, the new async/await mechanism can go horribly wrong if the programmer doesn't use it correctly. This can cause threads to start up, which is in fact slower than older .NET tech that had larger starting thread pools. You can view this with PerfView to see if it's your load issue.

In Go, the scheduler is smart enough to stop something even when it's not blocking on IO. This makes it more robust.

Of course, use what you need for when you need it. Rust definitely shines in some circumstances.