v.gen.c: fix compiling `go f(x)` for `x` of the same struct in different .v files with parallel cgen

vlib/v/gen/c/cgen.v

@@ -118,7 +118,7 @@ mut:
 	defer_profile_code     string
 	str_types              []StrType       // types that need automatic str() generation
 	generated_str_fns      []StrType       // types that already have a str() function
-	threaded_fns           []string  // for generating unique wrapper types and fns for `go xxx()`
+	threaded_fns           shared []string // for generating unique wrapper types and fns for `go xxx()`
 	waiter_fns             []string        // functions that wait for `go xxx()` to finish
 	auto_fn_definitions    []string        // auto generated functions defination list
 	sumtype_casting_fns    []SumtypeCastingFn
@@ -298,6 +298,7 @@ pub fn gen(files []&ast.File, table &ast.Table, pref &pref.Preferences) string {
 					inner_loop: &ast.EmptyStmt{}
 					field_data_type: ast.Type(global_g.table.find_type_idx('FieldData'))
 					array_sort_fn: global_g.array_sort_fn
+					threaded_fns: global_g.threaded_fns
 					done_optionals: global_g.done_optionals
 					is_autofree: global_g.pref.autofree
 				}
@@ -370,7 +371,6 @@ pub fn gen(files []&ast.File, table &ast.Table, pref &pref.Preferences) string {
 			global_g.nr_closures += g.nr_closures
 			global_g.has_main = global_g.has_main || g.has_main
 
-			global_g.threaded_fns << g.threaded_fns
 			global_g.waiter_fns << g.waiter_fns
 			global_g.auto_fn_definitions << g.auto_fn_definitions
 			global_g.anon_fn_definitions << g.anon_fn_definitions
@@ -6668,7 +6668,14 @@ fn (mut g Gen) go_expr(node ast.GoExpr) {
 		}
 	}
 	// Register the wrapper type and function
+	mut should_register := false
+	lock g.threaded_fns {
 		if name !in g.threaded_fns {
+			g.threaded_fns << name
+			should_register = true
+		}
+	}
+	if should_register {
 		g.type_definitions.writeln('\ntypedef struct $wrapper_struct_name {')
 		if expr.is_method {
 			styp := g.typ(expr.receiver_type)
@@ -6762,7 +6769,6 @@ fn (mut g Gen) go_expr(node ast.GoExpr) {
 			g.gowrappers.writeln('\treturn 0;')
 		}
 		g.gowrappers.writeln('}')
-		g.threaded_fns << name
 	}
 	if node.is_expr {
 		g.empty_line = false

vlib/v/tests/run_project_folders/go_fns_in_different_files_over_the_same_struct/f1.v

@@ -0,0 +1,6 @@
+module main
+
+fn f1() {
+	x := Abc{111}
+	go f(x)
+}

vlib/v/tests/run_project_folders/go_fns_in_different_files_over_the_same_struct/f2.v

@@ -0,0 +1,6 @@
+module main
+
+fn f2() {
+	x := Abc{222}
+	go f(x)
+}

vlib/v/tests/run_project_folders/go_fns_in_different_files_over_the_same_struct/main.v

@@ -0,0 +1,18 @@
+module main
+
+import time
+
+struct Abc {
+	x int
+}
+
+fn f(x Abc) {
+	println(x)
+}
+
+fn main() {
+	f1()
+	f2()
+	time.sleep(1 * time.second)
+	println('OK')
+}

vlib/v/tests/run_project_folders_test.v

@@ -24,13 +24,13 @@ fn test_v_profile_works() ? {
 	for folder_path in folder_paths {
 		local_path := folder_path.replace(vroot + os.path_separator, '').replace('\\',
 			'/')
-		println('..... $local_path/')
+		println('..... v run $local_path/')
 		res := os.execute('"$vexe" run $folder_path')
 		// eprintln('res: $res')
 		assert res.exit_code == 0
 		assert res.output.len > 0
 		assert res.output.contains('OK')
 		term.clear_previous_line()
-		println('${term.bold('OK')}    $local_path/')
+		println('${term.bold('OK')}    v run $local_path/')
 	}
 }