Introduce RegisterReaderHandlerWithConfig

It is the same as RegisterReaderHandler, but receives a copy of the
Config which is be needed to correctly encode the TSV. (For example
for the Location).

issue go-sql-driver#1416

infile.go

@@ -19,7 +19,7 @@ import (
 var (
 	fileRegister       map[string]bool
 	fileRegisterLock   sync.RWMutex
-	readerRegister     map[string]func() io.Reader
+	readerRegister     map[string]func(*Config) io.Reader
 	readerRegisterLock sync.RWMutex
 )
 
@@ -66,10 +66,21 @@ func DeregisterLocalFile(filePath string) {
 //	if err != nil {
 //	...
 func RegisterReaderHandler(name string, handler func() io.Reader) {
+	RegisterReaderHandlerWithConfig(name, func(*Config) io.Reader {
+		return handler()
+	})
+}
+
+// RegisterReaderHandlerWithConfig is like RegisterReaderHandler but the
+// callback receives a copy of the configuration.  The configuration should not
+// be modified.
+// This allows the caller to receive information about the connection, like the
+// timezone.
+func RegisterReaderHandlerWithConfig(name string, handler func(*Config) io.Reader) {
 	readerRegisterLock.Lock()
 	// lazy map init
 	if readerRegister == nil {
-		readerRegister = make(map[string]func() io.Reader)
+		readerRegister = make(map[string]func(*Config) io.Reader)
 	}
 
 	readerRegister[name] = handler
@@ -110,7 +121,7 @@ func (mc *mysqlConn) handleInFileRequest(name string) (err error) {
 		readerRegisterLock.RUnlock()
 
 		if inMap {
-			rdr = handler()
+			rdr = handler(mc.cfg.Clone())
 			if rdr != nil {
 				if cl, ok := rdr.(io.Closer); ok {
 					defer deferredClose(&err, cl)