Lock access to S.cache

GetRuntimeAddresses/symbolyze/symbolyze.go

@@ -335,9 +335,12 @@ func (S *Scanner) searchSymbolInPid(pid int) (offset uint64, found bool) {
 func (S *Scanner) findSymbolInELF(pathname string) (offset uint64, found bool) {
 
 	// 0. Return the value from the cache, if found.
+	S.RLock()
 	if offset, found = S.cache[pathname]; found {
+		S.RUnlock()
 		return offset, found
 	}
+	S.RUnlock()
 
 	// 1. Open the file with the ELF-parser
 	file, err := elf.Open(pathname)
@@ -390,7 +393,9 @@ func (S *Scanner) findSymbolInELF(pathname string) (offset uint64, found bool) {
 
 	// 6. Store this calculation in our cache so that we don't to touch
 	// this file again.
+	S.Lock()
 	S.cache[pathname] = vmOffset
+	S.Unlock()
 
 	return vmOffset, true
 }