why etcd serving as a standard go-module project failed to run "./build.sh" in root path

Bug report criteria

[X] This bug report is not security related, security issues should be disclosed privately via etcd maintainers.
[ ] This is not a support request or question, support requests or questions should be raised in the etcd discussion forums.
[ ] You have read the etcd bug reporting guidelines.
[ ] Existing open issues along with etcd frequently asked questions have been checked and this is not a duplicate.

What happened?

when run ./build.sh in etcd root directory, it failed and gave error: must be run from 'go.etcd.io/etcd/v3' module directory

the etcd project is cloned from github and didn't have any modification.

What did you expect to happen?

./build.sh run success at one shot

How can we reproduce it (as minimally and precisely as possible)?

step 1: git clone https://github.com/etcd-io/etcd.git git checkout release-3.5

step 2: cd etcd ./build.sh then errors: must be run from 'go.etcd.io/etcd/v3' module directory

Anything else we need to know?

env： x86_64 GNU/Linux

Etcd version (please run commands below)

```console $ etcd --version # paste output here $ etcdctl version # paste output here ``` nothing relevant to etcd and etcdctl, just the start up of building ectcd binary from etcd repo is not fluently.

Etcd configuration (command line flags or environment variables)

# paste your configuration here

Etcd debug information (please run commands below, feel free to obfuscate the IP address or FQDN in the output)

```console $ etcdctl member list -w table # paste output here $ etcdctl --endpoints= endpoint status -w table # paste output here ```

Relevant log output

No response

etcd-io / etcd