feat: support third party orm to interact with go-zero (#1286)

* fixes #987

* chore: fix test failure

* chore: add comments

* feat: support third party orm to interact with go-zero

* chore: refactor

zrpc/resolver/internal/subset_test.go

@@ -0,0 +1,54 @@
+package internal
+
+import (
+	"strconv"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/tal-tech/go-zero/core/mathx"
+)
+
+func TestSubset(t *testing.T) {
+	tests := []struct {
+		name string
+		set  int
+		sub  int
+	}{
+		{
+			name: "more vals to subset",
+			set:  100,
+			sub:  36,
+		},
+		{
+			name: "less vals to subset",
+			set:  100,
+			sub:  200,
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			var vals []string
+			for i := 0; i < test.set; i++ {
+				vals = append(vals, strconv.Itoa(i))
+			}
+
+			m := make(map[interface{}]int)
+			for i := 0; i < 1000; i++ {
+				set := subset(append([]string(nil), vals...), test.sub)
+				if test.sub < test.set {
+					assert.Equal(t, test.sub, len(set))
+				} else {
+					assert.Equal(t, test.set, len(set))
+				}
+
+				for _, val := range set {
+					m[val]++
+				}
+			}
+
+			assert.True(t, mathx.CalcEntropy(m) > 0.95)
+		})
+	}
+}