enum Gender {
    UNKNOWN = 0;
    MALE = 1;
    FEMALE = 2;
}

转换成 Golang 之后是这个样子：

type Person_Gender int32

const (
    Person_UNKNOWN Person_Gender = 0
    Person_MALE    Person_Gender = 1
    Person_FEMALE  Person_Gender = 2
)

// Enum value maps for Person_Gender.
var (
    Person_Gender_name = map[int32]string{
        0: "UNKNOWN",
        1: "MALE",
        2: "FEMALE",
    }
    Person_Gender_value = map[string]int32{
        "UNKNOWN": 0,
        "MALE":    1,
        "FEMALE":  2,
    }
)

func (x Person_Gender) Enum() *Person_Gender {
    p := new(Person_Gender)
    *p = x
    return p
}

func (x Person_Gender) String() string {
    return protoimpl.X.EnumStringOf(x.Descriptor(), protoreflect.EnumNumber(x))
}

func (Person_Gender) Descriptor() protoreflect.EnumDescriptor {
    return file_example_proto_enumTypes[0].Descriptor()
}

func (Person_Gender) Type() protoreflect.EnumType {
    return &file_example_proto_enumTypes[0]
}

func (x Person_Gender) Number() protoreflect.EnumNumber {
    return protoreflect.EnumNumber(x)
}

// Deprecated: Use Person_Gender.Descriptor instead.
func (Person_Gender) EnumDescriptor() ([]byte, []int) {
    return file_example_proto_rawDescGZIP(), []int{0, 0}
}