[Vendor] mssqldb: 2019-11-28 -> 2020-04-28 (#11364)

update go-mssqldb 2019-11-28 (1d7a30a10f73) -> 2020-04-28 (06a60b6afbbc)

vendor/github.com/denisenkom/go-mssqldb/accesstokenconnector.go

@@ -0,0 +1,51 @@
+// +build go1.10
+
+package mssql
+
+import (
+	"context"
+	"database/sql/driver"
+	"errors"
+	"fmt"
+)
+
+var _ driver.Connector = &accessTokenConnector{}
+
+// accessTokenConnector wraps Connector and injects a
+// fresh access token when connecting to the database
+type accessTokenConnector struct {
+	Connector
+
+	accessTokenProvider func() (string, error)
+}
+
+// NewAccessTokenConnector creates a new connector from a DSN and a token provider.
+// The token provider func will be called when a new connection is requested and should return a valid access token.
+// The returned connector may be used with sql.OpenDB.
+func NewAccessTokenConnector(dsn string, tokenProvider func() (string, error)) (driver.Connector, error) {
+	if tokenProvider == nil {
+		return nil, errors.New("mssql: tokenProvider cannot be nil")
+	}
+
+	conn, err := NewConnector(dsn)
+	if err != nil {
+		return nil, err
+	}
+
+	c := &accessTokenConnector{
+		Connector:           *conn,
+		accessTokenProvider: tokenProvider,
+	}
+	return c, nil
+}
+
+// Connect returns a new database connection
+func (c *accessTokenConnector) Connect(ctx context.Context) (driver.Conn, error) {
+	var err error
+	c.Connector.params.fedAuthAccessToken, err = c.accessTokenProvider()
+	if err != nil {
+		return nil, fmt.Errorf("mssql: error retrieving access token: %+v", err)
+	}
+
+	return c.Connector.Connect(ctx)
+}