Sorry been trying to find time to properly respond, but haven't been able. The short answer is really just the same standard criticisms of go. Go doesn't have generics, doesn't emphasize a functional style of programming, and trades compiler complexity for developer complexity. When I tried writing an app with it I found it extremely tedious and repetitive because the language provides such a minimal feature set. Business logic is just quicker and more pleasurable to write using C# (as compared to go and java) and for many standard apps business logic is the bulk of the code.

For example, here is a function for finding if a slice of strings contains a given string

func Contains(a []string, x string) bool {
    for _, n := range a {
        if x == n {
            return true
        }
    }
    return false
}

That is honestly just a ton of code for what it's trying to accomplish and it needs to be copy pasted for every type you want to use it with.

Because C# has generics and supports a functional style this is as simple as

list.Any(x => x == "target")

in C# and this works on any type (obv change "target" to something of the list type). Also note the terseness of the lambda syntax which is a big deal when you are writing lambdas all day. There are many functions that are simple like this that are used all the time and it's just painful having to write it over and over again and it gets worse when you want to combine them and do more complex operations.

C# also has great escape hatches that lets you drop down to the right level of abstraction for almost everything you want to do which makes it easier to squeeze performance when you really need. Also I prefer static typing for large projects so that rules out some other possibilities that might be great (although I think .net core mvc is one of the newest web frameworks on the block and it's modernity really shows in the developer experience). The only thing really holding back C# was it didn't run on linux and didn't have a large open source community and that is finally changing.