fix(analyzer): Support uppercase-letters in Go module version

plugins/package-managers/go/src/main/kotlin/GoMod.kt

@@ -454,7 +454,8 @@ private fun ModuleInfo.toSourceArtifact(): RemoteArtifact {
 }
 
 private fun ModuleInfo.toVcsInfo(): VcsInfo? {
-    val infoFile = goMod?.let { File(it).resolveSibling("$version.info") } ?: return null
+    val escapedVersion = escapeVersion(version)
+    val infoFile = goMod?.let { File(it).resolveSibling("$escapedVersion.info") } ?: return null
     val info = infoFile.inputStream().use { JSON.decodeFromStream<ModuleInfoFile>(it) }
     val type = info.origin.vcs?.let { VcsType.forName(it) }.takeIf { it == VcsType.GIT } ?: return null
 
@@ -484,3 +485,19 @@ internal fun parseWhyOutput(output: String): Set<String> {
 
     return usedModules
 }
+
+/**
+ * Module paths appear as substrings of file system paths in the module cache on the file system.
+ * Go does not rely on the file system to be case-sensitive. For this reason, Go has decided to
+ * replace every uppercase letter in file system paths with an exclamation mark followed by the
+ * letter's lowercase equivalent.
+ *
+ * Details behind the reasoning and implementation in Go can be found in the Go source code at
+ * [module.go](https://github.com/golang/go/blob/5b6d3dea8744311825fd544a73edb8d26d9c7e98/src/cmd/vendor/golang.org/x/mod/module/module.go#L33-L42C64)
+ */
+internal fun escapeVersion(version: String): String {
+    require("!" !in version) { "Module versions must not contain exclamation marks: $version" }
+    return version.replace(upperCaseCharRegex) { "!${it.value.lowercase()}" }
+}
+
+private val upperCaseCharRegex = Regex("[A-Z]")

plugins/package-managers/go/src/test/kotlin/GoModTest.kt

@@ -19,10 +19,12 @@
 
 package org.ossreviewtoolkit.plugins.packagemanagers.go
 
+import io.kotest.assertions.throwables.shouldThrow
 import io.kotest.core.spec.style.WordSpec
 import io.kotest.matchers.collections.beEmpty
 import io.kotest.matchers.collections.containExactlyInAnyOrder
 import io.kotest.matchers.should
+import io.kotest.matchers.shouldBe
 
 class GoModTest : WordSpec({
     "parseWhyOutput" should {
@@ -69,4 +71,21 @@ class GoModTest : WordSpec({
             )
         }
     }
+
+    "escapeVersion" should {
+        "escape uppercase letters" {
+            val version = "v0.1.0-MS4.0.20231102094829-08e0c3cd016c"
+            val escapedVersion = escapeVersion(version)
+
+            escapedVersion shouldBe "v0.1.0-!m!s4.0.20231102094829-08e0c3cd016c"
+        }
+
+        "throw exception if version string contains an exclamation mark" {
+            val version = "v1.0.0!"
+
+            shouldThrow<IllegalArgumentException> {
+                escapeVersion(version)
+            }
+        }
+    }
 })