package main

import (
    "C"
    "fmt"
)

func main() {}

//export Test
func Test(str *C.char) {
    fmt.Println("Hello from within Go")
    fmt.Println(fmt.Sprintf("A message from Go: %s", C.GoString(str)))
}

using System;
using System.Runtime.InteropServices;

namespace test
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello");
        Console.WriteLine(GoFunctions.Test("world"));
            Console.WriteLine("Goodbye.");
        }
    }


    static class GoFunctions
    {
    [DllImport(@<path to test.dll>, CharSet = CharSet.Unicode, CallingConvention = CallingConvention.StdCall)]
    public static extern string Test(GoString str);
    }
}

go build -buildmode=c-shared -o test.dll <path to go file>

Hello from within Go
A message from Go: w

panic: runtime error: growslice: cap out of range