fix: Support odd characters in pathnames for Go

Source/DafnyCore/Compilers/GoLang/Compiler-go.cs

@@ -56,7 +56,7 @@ private struct Import {
     protected override void EmitHeader(Program program, ConcreteSyntaxTree wr) {
       wr.WriteLine("// Dafny program {0} compiled into Go", program.Name);
 
-      ModuleName = MainModuleName = program.MainMethod != null ? "main" : Path.GetFileNameWithoutExtension(program.Name);
+      ModuleName = MainModuleName = program.MainMethod != null ? "main" : TransformToClassName(Path.GetFileNameWithoutExtension(program.Name));
 
       wr.WriteLine("package {0}", ModuleName);
       wr.WriteLine();
@@ -109,6 +109,9 @@ void EmitImports(ConcreteSyntaxTree wr, out ConcreteSyntaxTree importWriter, out
       }
     }
 
+    public static string TransformToClassName(string baseName) =>
+      Regex.Replace(baseName, "[^_A-Za-z0-9$]", "_");
+
     public override void EmitCallToMain(Method mainMethod, string baseName, ConcreteSyntaxTree wr) {
       var companion = TypeName_Companion(UserDefinedType.FromTopLevelDeclWithAllBooleanTypeParameters(mainMethod.EnclosingClass), wr, mainMethod.tok, mainMethod);
 

docs/dev/news/4257.fix

@@ -0,0 +1 @@
+Support odd characters in pathnames for Go