kvdb/sqlbase: fix build errors

We copy the `sqldb/sqlerrors.go` into `kvdb/sqlbase` to avoid import
cycles.

kvdb/sqlbase/db.go

@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"io"
 	"math"
+	"math/rand"
 	"sync"
 	"time"
 
@@ -37,12 +38,6 @@ const (
 	DefaultMaxRetryDelay = time.Second * 5
 )
 
-var (
-	// ErrRetriesExceeded is returned when a transaction is retried more
-	// than the max allowed valued without a success.
-	ErrRetriesExceeded = errors.New("db tx retries exceeded")
-)
-
 // Config holds a set of configuration options of a sql database connection.
 type Config struct {
 	// DriverName is the string that defines the registered sql driver that
@@ -238,7 +233,7 @@ func randRetryDelay(initialRetryDelay, maxRetryDelay time.Duration,
 	attempt int) time.Duration {
 
 	halfDelay := initialRetryDelay / 2
-	randDelay := prand.Int63n(int64(initialRetryDelay)) //nolint:gosec
+	randDelay := rand.Int63n(int64(initialRetryDelay)) //nolint:gosec
 
 	// 50% plus 0%-100% gives us the range of 50%-150%.
 	initialDelay := halfDelay + time.Duration(randDelay)
@@ -286,11 +281,11 @@ func (db *db) executeTransaction(f func(tx walletdb.ReadWriteTx) error,
 		select {
 		// Before we try again, we'll wait with a random backoff based
 		// on the retry delay.
-		case time.After(retryDelay):
+		case <-time.After(retryDelay):
 			return true
 
 		// If the daemon is shutting down, then we'll exit early.
-		case <-db.Context.Done():
+		case <-db.ctx.Done():
 			return false
 		}
 	}