更新：
我猜是TLDR;这是我的表的结构：

type EdgeDeviceOwnership struct {
    gorm.Model
    ID           string     `gorm:"primarykey; size:40;"`
    UserID       string     `gorm:"size:40; index; not null"`
    User         User       `gorm:"foreignKey:UserID; constraint:OnUpdate:CASCADE,OnDelete:CASCADE;"`
    EdgeDeviceID string     `gorm:"size:40; index; not null"`
    EdgeDevice   EdgeDevice `gorm:"foreignKey:EdgeDeviceID; constraint:OnUpdate:CASCADE,OnDelete:CASCADE;"`
    CreatedAt    time.Time  `gorm:"autoCreateTime:false"`
    UpdatedAt    time.Time  `gorm:"autoUpdateTime:false"`
}

get by id API现在工作正常，但是get all API仍然会抛出：
找到struct [github-name]/golang_grpc_server/proto的无效字段。EdgeDeviceOwnership的字段用户：为关系定义有效的外键或实现Valuer/Scanner接口
//UPDATE结束
在修复了我在this question中的上一个问题之后，我正在测试给我带来很多问题的模型/表是否工作正常。不幸的是，它没有。由于某种原因，当我为模型调用“getall”API时，我得到了这个错误。
找到struct [github-name]/golang_grpc_server/proto的无效字段。EdgeDeviceOwnership的字段用户：为关系定义有效的外键或实现Valuer/Scanner接口
这和我之前得到的错误很相似，这就是为什么我创建了上一个问题。仔细看，错误似乎来自我的protobuf。我的protoc命令将生成的文件放在protobuf所在的目录下，这让我很困惑。这些协议生成的结构是否以某种方式导致了问题？我不认为我们需要在gRPC中指定外键关系，对吗？
下面是我用来获取所有EdgeDeviceOwnership记录的代码：

pb "[github-name]/golang_grpc_server/proto"

func (*Server) GetEdgeDeviceOwnerships(ctx context.Context, req *pb.ReadEdgeDeviceOwnershipsRequest) (*pb.ReadEdgeDeviceOwnershipsResponse, error) {
    fmt.Println("Read EdgeDeviceOwnerships")
    edgeDeviceOwnerships := []*pb.EdgeDeviceOwnership{}
    res := DB.Preload(clause.Associations).Find(&edgeDeviceOwnerships)

    if res.RowsAffected == 0 {
        return nil, errors.New("EdgeDeviceOwnership not found")
    }

    return &pb.ReadEdgeDeviceOwnershipsResponse{
        EdgeDeviceOwnerships: edgeDeviceOwnerships,
    }, nil
}

下面是我的protoc命令，如果它有洞察力的话：
protoc --go_out=.--go_opt=paths=source_relative --go-grpc_out=.--go-grpc_opt=paths=source_relative proto/models.proto
更新：
我正在检查EdgeDeviceOwnership的get by id API，它似乎也有一些问题。它的代码看起来像这样：

func (*Server) GetEdgeDeviceOwnership(ctx context.Context, req *pb.ReadEdgeDeviceOwnershipRequest) (*pb.ReadEdgeDeviceOwnershipResponse, error) {
    fmt.Println("Read EdgeDeviceOwnership", req.GetId())
    var edgeDeviceOwnership models.EdgeDeviceOwnership
    res := DB.Preload("User").Preload("OwnedEdgeDevice").Find(&edgeDeviceOwnership, "id = ?", req.GetId())

    if res.RowsAffected == 0 {
        return nil, errors.New("EdgeDeviceOwnership not found")
    }

    pbUser := pb.User{
        FirstName: edgeDeviceOwnership.User.FirstName,
        LastName:  edgeDeviceOwnership.User.LastName,
        UserName:  edgeDeviceOwnership.User.UserName,
        Password:  edgeDeviceOwnership.User.Password,
    }

    pbEdgeDevice := pb.EdgeDevice{
        Status: pb.EdgeDeviceStatus(edgeDeviceOwnership.OwnedEdgeDevice.Status),
    }

    return &pb.ReadEdgeDeviceOwnershipResponse{
        EdgeDeviceOwnership: &pb.EdgeDeviceOwnership{
            Id:              edgeDeviceOwnership.ID,
            User:            &pbUser,
            OwnedEdgeDevice: &pbEdgeDevice,
        },
    }, nil
}

它返回一些东西，但缺少owned_edge_device。我更改了get all API以使用Preload()并预加载相同的字段，但它完全不适用于这些，并抛出了与上面相同的错误。
下面是客户端的相关代码：

ginGine.GET("/edge_device_ownership/:id", func(ctx *gin.Context) {
    id := ctx.Param("id")
    res, err := srvClient.GetEdgeDeviceOwnership(ctx, &pb.ReadEdgeDeviceOwnershipRequest{Id: id})
    if err != nil {
        ctx.JSON(http.StatusNotFound, gin.H{
            "message": err.Error(),
        })
        return
    }
    ctx.JSON(http.StatusOK, gin.H{
        "edge_device_ownership": res.EdgeDeviceOwnership,
    })
})

ginGine.GET("/edge_device_ownerships", func(ctx *gin.Context) {
    res, err := srvClient.GetEdgeDeviceOwnerships(ctx, &pb.ReadEdgeDeviceOwnershipsRequest{})
    if err != nil {
        ctx.JSON(http.StatusBadRequest, gin.H{
            "error": err,
        })
        return
    }
    ctx.JSON(http.StatusOK, gin.H{
        "edge_device_ownerships": res.EdgeDeviceOwnerships,
    })
})

为了清楚起见，我想，这里是服务器端的相关代码：

func (*Server) GetEdgeDeviceOwnership(ctx context.Context, req *pb.ReadEdgeDeviceOwnershipRequest) (*pb.ReadEdgeDeviceOwnershipResponse, error) {
    fmt.Println("Read EdgeDeviceOwnership", req.GetId())
    var edgeDeviceOwnership models.EdgeDeviceOwnership
    res := DB.Preload("User").Preload("OwnedEdgeDevice").Find(&edgeDeviceOwnership, "id = ?", req.GetId())

    if res.RowsAffected == 0 {
        return nil, errors.New("EdgeDeviceOwnership not found")
    }

    pbUser := pb.User{
        FirstName: edgeDeviceOwnership.User.FirstName,
        LastName:  edgeDeviceOwnership.User.LastName,
        UserName:  edgeDeviceOwnership.User.UserName,
        Password:  edgeDeviceOwnership.User.Password,
    }

    pbEdgeDevice := pb.EdgeDevice{
        Status: pb.EdgeDeviceStatus(edgeDeviceOwnership.OwnedEdgeDevice.Status),
    }

    return &pb.ReadEdgeDeviceOwnershipResponse{
        EdgeDeviceOwnership: &pb.EdgeDeviceOwnership{
            Id:              edgeDeviceOwnership.ID,
            User:            &pbUser,
            OwnedEdgeDevice: &pbEdgeDevice,
        },
    }, nil
}

func (*Server) GetEdgeDeviceOwnerships(ctx context.Context, req *pb.ReadEdgeDeviceOwnershipsRequest) (*pb.ReadEdgeDeviceOwnershipsResponse, error) {
    fmt.Println("Read EdgeDeviceOwnerships")
    edgeDeviceOwnerships := []*pb.EdgeDeviceOwnership{}
    res := DB.Preload("User").Preload("OwnedEdgeDevice").Find(&edgeDeviceOwnerships)

    if res.RowsAffected == 0 {
        return nil, errors.New("EdgeDeviceOwnership not found")
    }

    return &pb.ReadEdgeDeviceOwnershipsResponse{
        EdgeDeviceOwnerships: edgeDeviceOwnerships,
    }, nil
}

更新：
做了一些更新，使OwnedEdgeDevice到EdgeDevice，因为它看起来像你放在Preload（）中的字符串被假定为关系的表名，Status到Statusz，因为它看起来像status是MySQL上的保留字。我还使用了.Joins（），因为本质上EdgeDeviceOwnership只与User和EdgeDevice有一对一的关系，如果我理解正确的话。这是否意味着我必须同时执行.Joins()和.Preload()？不幸的是，有了那些变化，我仍然只得到我期望得到的一半。
更新：
看起来gorm有一个相当“破坏性”的行为，其中它剔除了具有零值的int字段。使用API，我以前只获取状态字段，它是一个整数字段。作为最后的玛丽，我想我也应该包括ID，看看是否真的返回了一些东西。而且它确实返回了ID！所以我尝试获取状态为1的记录，它也返回了1。所以至少现在“固定”了。我正在使用.Joins()作为该API。但是，不幸的是，对于使用.Joins()的get all API，它仍然会在标题上抛出该错误。