refactor(GoMod): Ignore the version constraint for go earlier

As of Go version 1.21.0 the module graph contains a version constraint
for the `go` version. As this does not represent a dependency it can be
filtered out. In fact the entry would be filtered out by the below
`graph.subgraph(vendorModules)`. However, the code crashes before
reaching that line. In particular, `parseModuleEntry(columns[1])` fails
because there is no `ModuleInfo` for "go".

Avoid that issue by ignoring the corresponding edge when parsing the
module graph. This is a preparation for upgrading to the latest Go
version.

Signed-off-by: Frank Viernau <[email protected]>

analyzer/src/main/kotlin/managers/GoMod.kt

@@ -182,7 +182,13 @@ class GoMod(
             val columns = line.splitOnWhitespace()
             require(columns.size == 2) { "Expected exactly one occurrence of ' ' on any non-blank line." }
 
-            val parent = parseModuleEntry(columns[0])
+            val parent = parseModuleEntry(columns[0]).apply {
+                // As of go version 1.21.1 the module graph contains a version constraint for the go version for
+                // the main project. The edge would be filtered out below by getVendorModules(). However, ignore
+                // it already here as there is no module info for 'go', so parseModuleEntry() would fail.
+                if (moduleInfo(name).main && columns[1].startsWith("go@")) return@forEach
+            }
+
             val child = parseModuleEntry(columns[1])
 
             if (moduleInfo(parent.name).main && moduleInfo(child.name).indirect) {