CODE EXAMPLE FOR TYPESCRIPT

Use AuthGuard with gRPC Metadata

import {Injectable, CanActivate, ExecutionContext} from '@nestjs/common';
import {Observable, throwError} from 'rxjs';
import {JwtService} from '@nestjs/jwt';

@Injectable()
export class GrpcAuthGuard implements CanActivate {

    constructor(private  jwtService: JwtService) {

    }

    canActivate(context: ExecutionContext): boolean | Promise<boolean> | Observable<boolean> {
        const type = context.getType();
        const prefix = 'Bearer ';
        let header;
        if(type==='rpc') {
            const metadata = context.getArgByIndex(1); // metadata
            if (!metadata) {
                return false;
            }
            header = metadata.get('Authorization')[0];
        }

        if (!header || !header.includes(prefix)) {
            return false;
        }

        const token = header.slice(header.indexOf(' ') + 1);
        try {
            const valid = this.jwtService.verify(token);
            return true;
        } catch (e) {
            return false;
        }
    }
}