refactor(stacktrace): remove unnecessary locking from segmentPrefixTrie

The segmentPrefixTrie follows a write-once-read-many pattern where all
writes occur during package initialization before any concurrent access.

After initialization, the trie is effectively immutable and can be safely
read by multiple goroutines without synchronization overhead.

Author: kakkoyun

internal/stacktrace/trie.go

@@ -145,9 +145,14 @@ func (t *prefixTrie) Clear() {
 // segmentPrefixTrie is a path segment-based trie optimized for "/" delimited paths.
 // It stores path segments (e.g., "github.com", "DataDog") as nodes instead of individual characters,
 // providing better memory efficiency and potentially faster lookups for module paths.
+//
+// Concurrency: This trie follows a write-once-read-many (WORM) pattern where all writes
+// occur during package initialization (init function) before any concurrent access begins.
+// After initialization, the trie is effectively immutable and can be safely read by multiple
+// goroutines without synchronization.
 type segmentPrefixTrie struct {
 	root *segmentTrieNode
-	mu   sync.RWMutex
+	// No mutex needed - structure is immutable after init()
 }
 
 // segmentTrieNode represents a single path segment node in the trie
@@ -165,15 +170,13 @@ func newSegmentPrefixTrie() *segmentPrefixTrie {
 	}
 }
 
-// Insert adds a prefix to the segment trie
+// Insert adds a prefix to the segment trie.
+// This method should only be called during initialization before any concurrent access.
 func (t *segmentPrefixTrie) Insert(prefix string) {
 	if prefix == "" {
 		return
 	}
 
-	t.mu.Lock()
-	defer t.mu.Unlock()
-
 	node := t.root
 	start := 0
 
@@ -197,14 +200,12 @@ func (t *segmentPrefixTrie) Insert(prefix string) {
 }
 
 // HasPrefix checks if the given string has any of the prefixes stored in the segment trie.
+// Safe for concurrent use after initialization.
 func (t *segmentPrefixTrie) HasPrefix(s string) (found bool) {
 	if s == "" {
 		return false
 	}
 
-	t.mu.RLock()
-	defer t.mu.RUnlock()
-
 	node := t.root
 	start := 0
 
@@ -230,11 +231,9 @@ func (t *segmentPrefixTrie) HasPrefix(s string) (found bool) {
 	return node.isEnd
 }
 
-// InsertAll adds multiple prefixes to the segment trie in a single operation
+// InsertAll adds multiple prefixes to the segment trie in a single operation.
+// This method should only be called during initialization before any concurrent access.
 func (t *segmentPrefixTrie) InsertAll(prefixes []string) {
-	t.mu.Lock()
-	defer t.mu.Unlock()
-
 	for _, prefix := range prefixes {
 		if prefix == "" {
 			continue
@@ -263,11 +262,9 @@ func (t *segmentPrefixTrie) InsertAll(prefixes []string) {
 	}
 }
 
-// Size returns the number of prefixes stored in the segment trie
+// Size returns the number of prefixes stored in the segment trie.
+// Safe for concurrent use after initialization.
 func (t *segmentPrefixTrie) Size() int {
-	t.mu.RLock()
-	defer t.mu.RUnlock()
-
 	return t.countSegmentPrefixes(t.root)
 }
 
@@ -289,11 +286,9 @@ func (t *segmentPrefixTrie) countSegmentPrefixes(node *segmentTrieNode) int {
 	return count
 }
 
-// Clear removes all prefixes from the segment trie
+// Clear removes all prefixes from the segment trie.
+// This method should only be called during initialization before any concurrent access.
 func (t *segmentPrefixTrie) Clear() {
-	t.mu.Lock()
-	defer t.mu.Unlock()
-
 	t.root = &segmentTrieNode{
 		children: make(map[string]*segmentTrieNode),
 	}