onDefinition is not found

[xg-github-00]

vscode-lua/server/src/server.ts

Line 68 in e3c2151

this.connection.onCompletion(pos => this.onCompletion(pos));

1. onDefinition is called when goto definition is used, but the realization is not found ,or how do you realize the "goto definition" function.
2. when I install 0.12.4 extension and use, in the LUA language server channel output, it shows the error below:
   (node:79644) [DEP0005] DeprecationWarning: Buffer() is deprecated due to security and usability issues. Please use the Buffer.alloc(), Buffer.allocUnsafe(), or Buffer.from() methods instead.

please help me to check the two problems, thank you very much~