Added wrapped error

This commit wraps the errors that could, under rare a occasion,
cause a panic. Allowing for a graceful recover by select
conditions.

Please see #82 for more info

buntdb.go

@@ -7,6 +7,7 @@ package buntdb
 import (
 	"bufio"
 	"errors"
+	"fmt"
 	"io"
 	"os"
 	"sort"
@@ -749,13 +750,13 @@ func (db *DB) Shrink() error {
 		if err := db.file.Close(); err != nil {
 			return err
 		}
-		// Any failures below here is really bad. So just panic.
+		// Any failures below here are really bad. So just panic.
 		if err := os.Rename(tmpname, fname); err != nil {
-			panic(err)
+			panicErr(err)
 		}
 		db.file, err = os.OpenFile(fname, os.O_CREATE|os.O_RDWR, 0666)
 		if err != nil {
-			panic(err)
+			panicErr(err)
 		}
 		pos, err := db.file.Seek(0, 2)
 		if err != nil {
@@ -766,6 +767,10 @@ func (db *DB) Shrink() error {
 	}()
 }
 
+func panicErr(err error) error {
+	panic(fmt.Errorf("buntdb: %w", err))
+}
+
 // readLoad reads from the reader and loads commands into the database.
 // modTime is the modified time of the reader, should be no greater than
 // the current time.Now().
@@ -1209,10 +1214,10 @@ func (tx *Tx) Commit() error {
 				// should be killed to avoid corrupting the file.
 				pos, err := tx.db.file.Seek(-int64(n), 1)
 				if err != nil {
-					panic(err)
+					panicErr(err)
 				}
 				if err := tx.db.file.Truncate(pos); err != nil {
-					panic(err)
+					panicErr(err)
 				}
 			}
 			tx.rollbackInner()

buntdb_test.go

@@ -2903,9 +2903,18 @@ func TestEstSize(t *testing.T) {
 		assert.Assert(estIntSize(-12) == 3)
 		assert.Assert(estIntSize(-124) == 4)
 	})
-	// t.Run("estI
-	// // dbi := dbItem{
-	// // 	key: "hello",
-	// // 	value: "
-	// // }
+}
+
+func TestWrappedError(t *testing.T) {
+	defer func() {
+		if err, ok := recover().(error); ok {
+			if strings.HasPrefix(err.Error(), "buntdb: ") {
+				err := errors.Unwrap(err)
+				if err.Error() != "my fake error" {
+					t.Fatal("!")
+				}
+			}
+		}
+	}()
+	panicErr(errors.New("my fake error"))
 }