fix golint issues in core/iox (#488)

core/iox/textlinescanner.go

@@ -6,6 +6,7 @@ import (
 	"strings"
 )
 
+// A TextLineScanner is a scanner that can scan lines from given reader.
 type TextLineScanner struct {
 	reader  *bufio.Reader
 	hasNext bool
@@ -13,6 +14,7 @@ type TextLineScanner struct {
 	err     error
 }
 
+// NewTextLineScanner returns a TextLineScanner with given reader.
 func NewTextLineScanner(reader io.Reader) *TextLineScanner {
 	return &TextLineScanner{
 		reader:  bufio.NewReader(reader),
@@ -20,6 +22,7 @@ func NewTextLineScanner(reader io.Reader) *TextLineScanner {
 	}
 }
 
+// Scan checks if scanner has more lines to read.
 func (scanner *TextLineScanner) Scan() bool {
 	if !scanner.hasNext {
 		return false
@@ -37,6 +40,7 @@ func (scanner *TextLineScanner) Scan() bool {
 	return true
 }
 
+// Line returns the next available line.
 func (scanner *TextLineScanner) Line() (string, error) {
 	return scanner.line, scanner.err
 }