Specify a custom dial function per config (#1527)

Specify a custom dial function per config instead of using RegisterDialContext.

Author: aaronjheng

connector.go

@@ -87,20 +87,25 @@ func (c *connector) Connect(ctx context.Context) (driver.Conn, error){
 mc.parseTime=mc.cfg.ParseTime
 
 // Connect to Server
-dialsLock.RLock()
-dial, ok:=dials[mc.cfg.Net]
-dialsLock.RUnlock()
-ifok{
-dctx:=ctx
-ifmc.cfg.Timeout>0{
-varcancel context.CancelFunc
-dctx, cancel=context.WithTimeout(ctx, c.cfg.Timeout)
-defercancel()
- }
-mc.netConn, err=dial(dctx, mc.cfg.Addr)
+dctx:=ctx
+ifmc.cfg.Timeout>0{
+varcancel context.CancelFunc
+dctx, cancel=context.WithTimeout(ctx, c.cfg.Timeout)
+defercancel()
+ }
+
+ifc.cfg.DialFunc!=nil{
+mc.netConn, err=c.cfg.DialFunc(dctx, mc.cfg.Net, mc.cfg.Addr)
  } else{
-nd:= net.Dialer{Timeout: mc.cfg.Timeout}
-mc.netConn, err=nd.DialContext(ctx, mc.cfg.Net, mc.cfg.Addr)
+dialsLock.RLock()
+dial, ok:=dials[mc.cfg.Net]
+dialsLock.RUnlock()
+ifok{
+mc.netConn, err=dial(dctx, mc.cfg.Addr)
+ } else{
+nd:= net.Dialer{}
+mc.netConn, err=nd.DialContext(dctx, mc.cfg.Net, mc.cfg.Addr)
+ }
  }
 iferr!=nil{
 returnnil, err

dsn.go

@@ -55,6 +55,8 @@ type Config struct{
 ReadTimeout time.Duration// I/O read timeout
 WriteTimeout time.Duration// I/O write timeout
 LoggerLogger// Logger
+// DialFunc specifies the dial function for creating connections
+DialFuncfunc(ctx context.Context, network, addrstring) (net.Conn, error)
 
 // boolean fields