diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0d4b4f5..d5f0a4a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -16,7 +16,7 @@ jobs:
 
     services:
       postgres:
-        image: "postgres:11"
+        image: "postgres:12"
         env:
           POSTGRES_PASSWORD: morph
           POSTGRES_DB: morph_test
@@ -31,7 +31,7 @@ jobs:
           - 6432:5432
 
       mysql:
-        image: "mysql:5.7"
+        image: "mysql:8"
         env:
           MYSQL_DATABASE: morph_test
           MYSQL_USER: morph
diff --git a/cmd/morph/morph.go b/cmd/morph/morph.go
index 00d9919..f6eedd9 100644
--- a/cmd/morph/morph.go
+++ b/cmd/morph/morph.go
@@ -20,5 +20,6 @@ func main() {
 			morph.ErrorLogger.Fprintf(os.Stderr, "An Error Occurred:\n")
 		}
 		_, _ = morph.ErrorLoggerLight.Fprintf(os.Stderr, "--> %v\n", err)
+		os.Exit(1)
 	}
 }
diff --git a/docker-compose.yml b/docker-compose.yml
index 948a02c..d4a1d20 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -1,7 +1,7 @@
 version: '3.1'
 services:
   postgres:
-    image: postgres
+    image: postgres:12
     restart: always
     ports:
       - "6432:5432"
@@ -10,7 +10,7 @@ services:
       POSTGRES_DB: morph_test
       POSTGRES_USER: morph
   mysql:
-    image: "mysql:5.7"
+    image: "mysql:8"
     restart: always
     ports:
       - "3307:3306"
diff --git a/drivers/driver.go b/drivers/driver.go
index a39cdde..2a2ab99 100644
--- a/drivers/driver.go
+++ b/drivers/driver.go
@@ -5,19 +5,27 @@ import (
 )
 
 type Config struct {
+	// MigrationsTableName is the name of the table that will store the migrations.
 	MigrationsTable string
 	// StatementTimeoutInSecs is used to set a timeout for each migration file.
 	// Set below zero to disable timeout. Zero value will result in default value, which is 60 seconds.
 	StatementTimeoutInSecs int
-	MigrationMaxSize       int
+	// MigrationMaxSize is the maximum size of a migration file in bytes.
+	MigrationMaxSize int
 }
 
+// Driver is the interface that should be implemented by all drivers.
+// The driver is responsible for applying migrations to the database.
 type Driver interface {
 	Ping() error
 	// Close closes the underlying db connection. If the driver is created via Open() function
 	// this method will also going to call Close() on the sql.db instance.
 	Close() error
+	// Apply should apply the migration to the database. If saveVersion is true, the driver should
+	// save the migration version in the database.
 	Apply(migration *models.Migration, saveVersion bool) error
+	// AppliedMigrations should return a list of applied migrations.
+	// Ideally migrations should be sorted by version.
 	AppliedMigrations() ([]*models.Migration, error)
 	// SetConfig should be used to set the driver configuration. The key is the name of the configuration
 	// This method should return an error if the key is not supported.
diff --git a/drivers/lock.go b/drivers/lock.go
index 9861bd3..195a2e3 100644
--- a/drivers/lock.go
+++ b/drivers/lock.go
@@ -63,7 +63,7 @@ func NextWaitInterval(lastWaitInterval time.Duration, err error) time.Duration {
 }
 
 type Locker interface {
-	// Lock locks m unless the context is canceled. If the mutex is already locked by any other
+	// Lock refreshes the lock unless the context is canceled. If the mutex is already locked by any other
 	// instance, including the current one, the calling goroutine blocks until the mutex can be locked,
 	// or the context is canceled.
 	//
@@ -75,10 +75,3 @@ type Locker interface {
 type Lockable interface {
 	NewMutex(key string, logger Logger) (Locker, error)
 }
-
-// IsLockable returns whether the given instance satisfies
-// drivers.Lockable or not.
-func IsLockable(x interface{}) bool {
-	_, ok := x.(Lockable)
-	return ok
-}