allow to set http client

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

options.go

@@ -1,12 +1,19 @@
 package vault
 
 import (
+	"net/http"
 	"time"
 
 	"github.com/hashicorp/vault/api"
 	"go.unistack.org/micro/v3/config"
 )
 
+type httpClientKey struct{}
+
+func HTTPClient(c *http.Client) config.Option {
+	return config.SetOption(httpClientKey{}, c)
+}
+
 type configKey struct{}
 
 func Config(cfg *api.Config) config.Option {

vault.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"net/http"
 	"time"
 
 	"github.com/hashicorp/vault/api"
@@ -46,6 +47,10 @@ func (c *vaultConfig) Init(opts ...config.Option) error {
 			cfg = v
 		}
 
+		if v, ok := c.opts.Context.Value(httpClientKey{}).(*http.Client); ok {
+			cfg.HttpClient = v
+		}
+
 		if v, ok := c.opts.Context.Value(timeoutKey{}).(time.Duration); ok {
 			cfg.Timeout = v
 		}