update to use new io.Seek consts, require min go1.7

sum.go

@@ -7,7 +7,6 @@ import (
 	"fmt"
 	"hash"
 	"io"
-	"os"
 )
 
 // Sum creates a checksum of the audio file data provided by the io.ReadSeeker which is metadata
@@ -18,7 +17,7 @@ func Sum(r io.ReadSeeker) (string, error) {
 		return "", err
 	}
 
-	_, err = r.Seek(-11, os.SEEK_CUR)
+	_, err = r.Seek(-11, io.SeekCurrent)
 	if err != nil {
 		return "", fmt.Errorf("could not seek back to original position: %v", err)
 	}
@@ -75,7 +74,7 @@ func SumAtoms(r io.ReadSeeker) (string, error) {
 		switch name {
 		case "meta":
 			// next_item_id (int32)
-			_, err := r.Seek(4, os.SEEK_CUR)
+			_, err := r.Seek(4, io.SeekCurrent)
 			if err != nil {
 				return "", err
 			}
@@ -93,7 +92,7 @@ func SumAtoms(r io.ReadSeeker) (string, error) {
 			return hashSum(h), nil
 		}
 
-		_, err = r.Seek(int64(size-8), os.SEEK_CUR)
+		_, err = r.Seek(int64(size-8), io.SeekCurrent)
 		if err != nil {
 			return "", fmt.Errorf("error reading '%v' tag: %v", name, err)
 		}
@@ -101,12 +100,12 @@ func SumAtoms(r io.ReadSeeker) (string, error) {
 }
 
 func sizeToEndOffset(r io.ReadSeeker, offset int64) (int64, error) {
-	n, err := r.Seek(-128, os.SEEK_END)
+	n, err := r.Seek(-128, io.SeekEnd)
 	if err != nil {
 		return 0, fmt.Errorf("error seeking end offset (%d bytes): %v", offset, err)
 	}
 
-	_, err = r.Seek(-n, os.SEEK_CUR)
+	_, err = r.Seek(-n, io.SeekCurrent)
 	if err != nil {
 		return 0, fmt.Errorf("error seeking back to original position: %v", err)
 	}
@@ -142,7 +141,7 @@ func SumID3v2(r io.ReadSeeker) (string, error) {
 		return "", fmt.Errorf("error reading ID3v2 header: %v", err)
 	}
 
-	_, err = r.Seek(int64(header.Size), os.SEEK_CUR)
+	_, err = r.Seek(int64(header.Size), io.SeekCurrent)
 	if err != nil {
 		return "", fmt.Errorf("error seeking to end of ID3V2 header: %v", err)
 	}
@@ -211,7 +210,7 @@ func skipFLACMetadataBlock(r io.ReadSeeker) (last bool, err error) {
 		return
 	}
 
-	_, err = r.Seek(int64(blockLen), os.SEEK_CUR)
+	_, err = r.Seek(int64(blockLen), io.SeekCurrent)
 	return
 }