feat: improve Docker configuration and detection handling (#242)

- Pass `cfg` to `envcheck.CheckIfDockerRunning` function
- Add `Docker` struct to `config.go` for Docker configuration
- Update `config.example.yaml` with `docker` configuration options
- Modify `CheckIfDockerRunning` in `docker.go` to use Docker host from config if provided

Signed-off-by: appleboy <appleboy.tw@gmail.com>

Reviewed-on: https://gitea.com/gitea/act_runner/pulls/242
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-by: wxiaoguang <wxiaoguang@noreply.gitea.com>
Co-authored-by: appleboy <appleboy.tw@gmail.com>
Co-committed-by: appleboy <appleboy.tw@gmail.com>

internal/pkg/envcheck/docker.go

@@ -7,12 +7,21 @@ import (
 	"context"
 	"fmt"
 
+	"gitea.com/gitea/act_runner/internal/pkg/config"
+
 	"github.com/docker/docker/client"
 )
 
-func CheckIfDockerRunning(ctx context.Context) error {
-	// TODO: if runner support configures to use docker, we need config.Config to pass in
-	cli, err := client.NewClientWithOpts(client.FromEnv)
+func CheckIfDockerRunning(ctx context.Context, cfg *config.Config) error {
+	opts := []client.Opt{
+		client.FromEnv,
+	}
+
+	if cfg.Docker.Host != "" {
+		opts = append(opts, client.WithHost(cfg.Docker.Host))
+	}
+
+	cli, err := client.NewClientWithOpts(opts...)
 	if err != nil {
 		return err
 	}