Dockerfile 会报错: "go.sum" not found"

```

=> ERROR [builder 3/6] COPY go.mod go.sum ./ 0.0s

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> [builder 3/6] COPY go.mod go.sum ./:

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Dockerfile:8

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6 |

7 | # 复制 go mod 和 sum 文件

8 | >>> COPY go.mod go.sum ./

9 |

10 | # 下载依赖

--------------------

ERROR: failed to solve: failed to compute cache key: failed to calculate checksum of ref c383ecbb-be5e-435a-a15d-757f00bad3cc::oyxt0cebvysj0m8zybusi177p: "/go.sum": not found