feat(config): watch config file and hot-reload router without restart

[tao12345666333]

What type of PR is this?

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #82

Release Notes: Yes/No

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[rootfs]

can you add a followup pr to test config file update under different scenarios?

[tao12345666333]

OK

[tao12345666333]

#92 for tracking

[github-actions]

👥 vLLM Semantic Team Notification

The following members have been identified for the changed files in this PR and have been automatically assigned:

📁 src

Owners: @rootfs, @Xunzhuo, @wangchen615
Files changed:

• src/semantic-router/pkg/config/parse_configfile_test.go
• src/semantic-router/go.mod
• src/semantic-router/go.sum
• src/semantic-router/pkg/config/config.go
• src/semantic-router/pkg/extproc/router.go
• src/semantic-router/pkg/extproc/server.go

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🎉 Thanks for your contributions!

This comment was automatically generated based on the OWNER files in the repository.

[yuluo-yx]

hi, @tao12345666333 @rootfs

for this regard, I have an idea, why don't we use viper directly? 🤔

https://github.com/spf13/viper

[tao12345666333]

for this regard, I have an idea, why don't we use viper directly? 🤔

https://github.com/spf13/viper

I don't want to introduce viper because it's over-engineered and has some irrelevant dependencies.

Here we need more precise control, and we don't need the complex templates and environment variable binding features in viper.