golang: tests: Normalize paths to use / delimiter in doctests's got

Else on Windows e.g. test_defer_excchain_traceback fails as

    E           Failed: not equal:
    E           Differences (unified diff with -expected +actual):
    E               @@ -1,8 +1,8 @@
    E                Traceback (most recent call last):
    E               -  File "PYGOLANG/golang/golang_test.py", line ..., in test_defer_excchain_traceback
    E               +  File "PYGOLANG\golang\golang_test.py", line 1524, in test_defer_excchain_traceback
    E                    alpha()
    E               -  File "PYGOLANG/golang/golang_test.py", line ..., in alpha
    E               +  File "PYGOLANG\golang\golang_test.py", line 1521, in alpha
    E                    beta()
    E               -  File "PYGOLANG/golang/golang_test.py", line ..., in beta
    E               +  File "PYGOLANG\golang\golang_test.py", line 1520, in beta
    E                    raise RuntimeError("gamma")
    E                RuntimeError: gamma

golang/golang_test.py

@@ -1807,6 +1807,13 @@ def assertDoc(want, got):
     got = got.replace(dir_pygolang,  "PYGOLANG") # /home/x/.../pygolang -> PYGOLANG
     got = got.replace(udir_pygolang, "PYGOLANG") # ~/.../pygolang       -> PYGOLANG
 
+    # got: normalize PYGOLANG\a\b\c -> PYGOLANG/a/b/c
+    #                a\b\c\d.py  -> a/b/c/d.py
+    def _(m):
+        return m.group(0).replace(os.path.sep, '/')
+    got = re.sub(r"(?<=PYGOLANG)[^\s]+(?=\s)",  _, got)
+    got = re.sub(r"([\w\\\.]+)(?=\.py)",        _, got)
+
     # want: process conditionals
     # PY39(...) -> ...   if py ≥ 3.9 else ø  (inline)
     # `... +PY39` -> ... if py ≥ 3.9 else ø  (whole line)