Build go function fails if there are more than main.go in src

### How did you install the Amplify CLI?

yarn

### If applicable, what version of Node.js are you using?

20

### Amplify CLI Version

12.11.1

### What operating system are you using?

Ubuntu

### Did you make any manual changes to the cloud resources managed by Amplify? Please describe the changes made.

No

### Describe the bug

This change [here](https://github.com/aws-amplify/amplify-cli/pull/13671/files#diff-9e8ed84544b6574832f1d34bde8bc4fffff3558a54806adb09b4884758ff618aR105) fails go function build if there are more than main.go in src.

### Expected behavior

Go function should be built

### Reproduction steps

1. Create a lambda function using go
2. in main.go use a function defined in another.go
3. Build will fail

### Project Identifier

_No response_

### Log output

_No response_

### Additional information

_No response_

### Before submitting, please confirm:

- [X] I have done my best to include a minimal, self-contained set of instructions for consistently reproducing the issue.
- [X] I have removed any sensitive information from my code snippets and submission.