factor out unix domain grpc client (#463)

agent/agentClient/agentClient.go

@@ -0,0 +1,33 @@
+package agentClient
+
+import (
+	"context"
+	"github.com/openziti/zrok/agent/agentGrpc"
+	"github.com/openziti/zrok/environment/env_core"
+	"github.com/openziti/zrok/tui"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
+	"google.golang.org/grpc/resolver"
+	"net"
+)
+
+func NewClient(root env_core.Root) (client agentGrpc.AgentClient, conn *grpc.ClientConn, err error) {
+	agentSocket, err := root.AgentSocket()
+	if err != nil {
+		tui.Error("error getting agent socket", err)
+	}
+
+	opts := []grpc.DialOption{
+		grpc.WithContextDialer(func(_ context.Context, addr string) (net.Conn, error) {
+			return net.Dial("unix", addr)
+		}),
+		grpc.WithTransportCredentials(insecure.NewCredentials()),
+	}
+	resolver.SetDefaultScheme("passthrough")
+	conn, err = grpc.NewClient(agentSocket, opts...)
+	if err != nil {
+		tui.Error("error connecting to agent socket", err)
+	}
+
+	return agentGrpc.NewAgentClient(conn), conn, nil
+}