M1 Mac Support for Testing

The library/mysql container doesn't support arm64/v8,
which caused the tests to not be runnable on M1 Macs.

This commit adds two ways to solve this:

1. TestDB now has a SkippedArchs property, which
allows certain Docker containers to be tagged to
not support certain runtime.GOARCH strings. These
cause a skipped test when used.
2. The MySQL test container was switched from
libary/mysql to mysql/mysql-server (the one produced
directly by the MySQL team), which *does* support
arm64/v8, but only on the latest MySQL 8 version.

main_test.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"runtime"
 	"sync"
 	"testing"
 
@@ -33,7 +34,9 @@ func TestMain(m *testing.M) {
 		testDB := TestDBs[name]
 		wg.Add(1)
 		go func() {
-			testDB.Init(pool)
+			if testDB.IsRunnable() {
+				testDB.Init(pool)
+			}
 			wg.Done()
 		}()
 	}
@@ -66,7 +69,11 @@ func withEachDialect(t *testing.T, f func(t *testing.T, d Dialect)) {
 func withEachTestDB(t *testing.T, f func(t *testing.T, tdb *TestDB)) {
 	for dbName, tdb := range TestDBs {
 		t.Run(dbName, func(t *testing.T) {
-			f(t, tdb)
+			if tdb.IsRunnable() {
+				f(t, tdb)
+			} else {
+				t.Skipf("Not runnable on %s", runtime.GOARCH)
+			}
 		})
 	}
 }

schema_test.go

@@ -44,7 +44,7 @@ var TestDBs map[string]*TestDB = map[string]*TestDB{
 	"mysql:latest": {
 		Dialect:    MySQL,
 		Driver:     MySQLDriverName,
-		DockerRepo: "mysql",
+		DockerRepo: "mysql/mysql-server",
 		DockerTag:  "latest",
 	},
 	"mariadb:latest": {

testdb_test.go

@@ -6,6 +6,7 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
+	"runtime"
 	"testing"
 
 	"github.com/ory/dockertest"
@@ -16,12 +17,13 @@ import (
 // to run database migration tests.
 //
 type TestDB struct {
-	Dialect    Dialect
-	Driver     string
-	DockerRepo string
-	DockerTag  string
-	Resource   *dockertest.Resource
-	path       string
+	Dialect      Dialect
+	Driver       string
+	DockerRepo   string
+	DockerTag    string
+	Resource     *dockertest.Resource
+	SkippedArchs []string
+	path         string
 }
 
 func (c *TestDB) Username() string {
@@ -80,6 +82,15 @@ func (c *TestDB) DockerEnvars() []string {
 	}
 }
 
+func (c *TestDB) IsRunnable() bool {
+	for _, skippedArch := range c.SkippedArchs {
+		if skippedArch == runtime.GOARCH {
+			return false
+		}
+	}
+	return true
+}
+
 // Path computes the full path to the database on disk (applies only to SQLite
 // instances).
 func (c *TestDB) Path() string {