command: Fix stale lock after running add

internal/command/add.go

@@ -106,6 +106,14 @@ func (c *AddCommand) Run(rawArgs []string) int {
 		return 1
 	}
 
+	// Successfully creating the context can result in a lock, so ensure we release it
+	defer func() {
+		diags := opReq.StateLocker.Unlock()
+		if diags.HasErrors() {
+			c.showDiagnostics(diags)
+		}
+	}()
+
 	// load the configuration to verify that the resource address doesn't
 	// already exist in the config.
 	var module *configs.Module

internal/command/add_test.go

@@ -3,6 +3,7 @@ package command
 import (
 	"fmt"
 	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 
@@ -592,4 +593,7 @@ resource "test_instance" "new" {
 		t.Fatalf("wrong output:\n%s", cmp.Diff(expected, output.Stdout()))
 	}
 
+	if _, err := os.Stat(filepath.Join(td, ".terraform.tfstate.lock.info")); !os.IsNotExist(err) {
+		t.Fatal("state left locked after add")
+	}
 }