Improve sync method. Improve docs.

README.md

@@ -8,6 +8,7 @@ GNU gettext utilities for Go.
 - It works with UTF-8 encoding as it's the default for Go language. 
 - Supports pluralization rules.
 - Ready to use inside Go templates.
+- Safe for concurrent use accross multiple goroutines.
 - Language codes are automatically simplified from the form "en_UK" to "en" if the formed isn't available.
 - Unit tests available
 
@@ -34,6 +35,38 @@ Refer to the Godoc package documentation at (https://godoc.org/github.com/leonel
 
 
 
+# About translation function names
+
+The standard GNU gettext defines helper functions that maps to the gettext() function and it's widely adopted by most implementations. 
+
+The basic translation function is usually _() in the form: 
+
+```
+_("Translate this")
+``` 
+
+In Go, this can't be implemented by a reusable package as the function name has to start with a capital letter in order to be exported. 
+
+Each implementation of this package can declare this helper functions inside their own packages if this function naming are desired/needed: 
+
+```go
+package main
+
+import "github.com/leonelquinteros/gotext"
+
+func _(str string, vars ...interface{}) string {
+    return gotext.Get(str, vars...)
+}
+
+``` 
+
+This is valid and can be used within a package.
+
+In normal conditions the Go compiler will optimize the calls to _() by replacing its content in place of the function call to reduce the function calling overhead. 
+This is a normal Go compiler behaviour.  
+
+
+
 # Usage examples
 
 ## Using package for single language/domain settings

po.go

@@ -75,11 +75,10 @@ func (po *Po) ParseFile(f string) {
 
 // Parse loads the translations specified in the provided string (str)
 func (po *Po) Parse(str string) {
-	po.Lock()
-	defer po.Unlock()
-
 	if po.translations == nil {
+		po.Lock()
 		po.translations = make(map[string]*translation)
+		po.Unlock()
 	}
 
 	lines := strings.Split(str, "\n")
@@ -103,7 +102,9 @@ func (po *Po) Parse(str string) {
 		// Buffer msgid and continue
 		if strings.HasPrefix(l, "msgid") && !strings.HasPrefix(l, "msgid_plural") {
 			// Save current translation buffer.
+			po.Lock()
 			po.translations[tr.id] = tr
+			po.Unlock()
 
 			// Flush buffer
 			tr = newTranslation()
@@ -156,7 +157,9 @@ func (po *Po) Parse(str string) {
 
 	// Save last translation buffer.
 	if tr.id != "" {
+		po.Lock()
 		po.translations[tr.id] = tr
+		po.Unlock()
 	}
 }