Fix golang purl issue

We shoul add a leading v in version for golang purls download URL where purl's version misses a leading v

Signed-off-by: Tushar Goel <tushar.goel.dav@gmail.com>

Author: TG1999

src/packageurl/contrib/purl2url.py

@@ -478,6 +478,9 @@ def build_golang_download_url(purl):
     ename = escape_golang_path(name)
     eversion = escape_golang_path(version)
 
+    if not eversion.startswith("v"):
+        eversion = "v" + eversion
+
     if name and version:
         return f"https://proxy.golang.org/{ename}/@v/{eversion}.zip"
 

tests/contrib/test_purl2url.py

@@ -102,6 +102,7 @@ def test_purl2url_get_download_url():
         "pkg:golang/xorm.io/xorm@v0.8.2": "https://proxy.golang.org/xorm.io/xorm/@v/v0.8.2.zip",
         "pkg:golang/gopkg.in/ldap.v3@v3.1.0": "https://proxy.golang.org/gopkg.in/ldap.v3/@v/v3.1.0.zip",
         "pkg:golang/example.com/M.v3@v3.1.0": "https://proxy.golang.org/example.com/!m.v3/@v/v3.1.0.zip",
+        "pkg:golang/golang.org/x/oauth2@0.29.0": "https://proxy.golang.org/golang.org/x/oauth2/@v/v0.29.0.zip",
         "pkg:pub/http@0.13.3": "https://pub.dev/api/archives/http-0.13.3.tar.gz",
         "pkg:swift/github.com/Alamofire/Alamofire@5.4.3": "https://github.com/Alamofire/Alamofire/archive/5.4.3.zip",
         "pkg:swift/github.com/RxSwiftCommunity/RxFlow@2.12.4": "https://github.com/RxSwiftCommunity/RxFlow/archive/2.12.4.zip",