interp: recover in Eval and EvalPath

Now Eval() and EvalPath() recover from internal panic and
return it as error with call stacks.

This fixes the case where user code calls os.Exit(1), which is
converted to panic() and breaks down the program.

interp/interp.go

@@ -498,13 +498,29 @@ func (interp *Interpreter) resizeFrame() {
 // Eval evaluates Go code represented as a string. Eval returns the last result
 // computed by the interpreter, and a non nil error in case of failure.
 func (interp *Interpreter) Eval(src string) (res reflect.Value, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			var pc [64]uintptr
+			n := runtime.Callers(1, pc[:])
+			err = Panic{Value: r, Callers: pc[:n], Stack: debug.Stack()}
+		}
+	}()
+
 	return interp.eval(src, "", true)
 }
 
 // EvalPath evaluates Go code located at path and returns the last result computed
 // by the interpreter, and a non nil error in case of failure.
 // The main function of the main package is executed if present.
 func (interp *Interpreter) EvalPath(path string) (res reflect.Value, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			var pc [64]uintptr
+			n := runtime.Callers(1, pc[:])
+			err = Panic{Value: r, Callers: pc[:n], Stack: debug.Stack()}
+		}
+	}()
+
 	if !isFile(interp.opt.filesystem, path) {
 		_, err := interp.importSrc(mainID, path, NoTest)
 		return res, err
@@ -581,14 +597,7 @@ func (interp *Interpreter) EvalWithContext(ctx context.Context, src string) (ref
 
 	done := make(chan struct{})
 	go func() {
-		defer func() {
-			if r := recover(); r != nil {
-				var pc [64]uintptr
-				n := runtime.Callers(1, pc[:])
-				err = Panic{Value: r, Callers: pc[:n], Stack: debug.Stack()}
-			}
-			close(done)
-		}()
+		defer close(done)
 		v, err = interp.Eval(src)
 	}()