proc/native,proc/gdbserial: set selectedGoroutine after StepInstruction

When stepping through runtime sometimes the current goroutine will
change. It is impossible to handle this in Next, Step and StepOut but
StepInstruction can reset the current goroutine correctly.

pkg/proc/gdbserial/gdbserver.go

@@ -642,7 +642,14 @@ func (p *Process) StepInstruction() error {
 	if err != nil {
 		return err
 	}
-	return thread.SetCurrentBreakpoint()
+	err = thread.SetCurrentBreakpoint()
+	if err != nil {
+		return err
+	}
+	if g, _ := proc.GetG(thread); g != nil {
+		p.selectedGoroutine = g
+	}
+	return nil
 }
 
 func (p *Process) SwitchThread(tid int) error {

pkg/proc/native/proc.go

@@ -316,7 +316,14 @@ func (dbp *Process) StepInstruction() (err error) {
 	if err != nil {
 		return err
 	}
-	return thread.SetCurrentBreakpoint()
+	err = thread.SetCurrentBreakpoint()
+	if err != nil {
+		return err
+	}
+	if g, _ := proc.GetG(thread); g != nil {
+		dbp.selectedGoroutine = g
+	}
+	return nil
 }
 
 // SwitchThread changes from current thread to the thread specified by `tid`.