fix(lib/output): check if channels aren't nil before printing

Author: Luis Silva

Diff for: src/lib/errors.go

@@ -5,3 +5,15 @@ type TransactionNotSupportedError struct{}
 func (e *TransactionNotSupportedError) Error() string {
 	return "transactions are only supported in the shell using semicolons to separate each statement.\nFor example: \"BEGIN; [your SQL statements]; END\""
 }
+
+type InvalidStatementsResult struct{}
+
+func (e *InvalidStatementsResult) Error() string {
+	return "invalid statements result"
+}
+
+type UnableToPrintStatementResult struct{}
+
+func (e *UnableToPrintStatementResult) Error() string {
+	return "unable to print statement result. You should check if its an error before printing it"
+}

Diff for: src/lib/output.go

@@ -13,6 +13,10 @@ import (
 )
 
 func PrintStatementsResult(statementsResult statementsResult, outF io.Writer, withoutHeader bool) error {
+	if statementsResult.StatementResultCh == nil {
+		return &InvalidStatementsResult{}
+	}
+
 	for statementResult := range statementsResult.StatementResultCh {
 		if statementResult.Err != nil {
 			return statementResult.Err
@@ -27,6 +31,10 @@ func PrintStatementsResult(statementsResult statementsResult, outF io.Writer, wi
 }
 
 func PrintStatementResult(statementResult statementResult, outF io.Writer, withoutHeader bool) error {
+	if statementResult.RowCh == nil {
+		return &UnableToPrintStatementResult{}
+	}
+
 	if len(statementResult.ColumnNames) == 0 {
 		return nil
 	}