npm install -g react-native-create-library

react-native-create-library --package-indentifier com.wesleysd1989.reactnative --plataforms android,ios comunicacao-nativa

no arquivo package.json coloque a versao do react-native no meu caso coloquei versão 0.61.4.

"peerDependencies": {
    "react-native": "0.61.4"
  }

@ReactMethod
  public void checkBridge(Promise promise) {
    promise.resolve("modulo nativo android");
  }

RCT_EXPORT_METHOD(checkBridge:(RCTPromiseResolveBlock)resolve
                 rejecter:(RCTPromiseRejectBlock)reject)
{
  resolve(@"modulo nativo ios");
}

dentro do projeto na pasta ios terá um arquivo <nome_da_lib>.podspec, mova esse arquivo para raiz do projeto. edite as seguintes tags.

mude de ->
s.homepage     = ""
para -> 
s.homepage     = "https://github.com/wesleysd1989/comunicacao-nativa" //esse link e do seu diretorio do github

mude de ->
s.source       = { :git => "https://github.com/author/comunicacao-nativa.git", :tag => "master" }
s.source_files  = "RNTComunicacaoNativa/**/*.{h,m}"
para ->
s.source       = { :git => "https://github.com/wesleysd1989/comunicacao-nativa", :tag => "master" } //esse link e do seu diretorio do github
s.source_files = "ios/*.{h,m}"

inclua o seguinte method na lib IOS - ios/RNComunicacaoNativa.m

RCT_EXPORT_METHOD(checkBridge:(RCTPromiseResolveBlock)resolve
                 rejecter:(RCTPromiseRejectBlock)reject)
{
  resolve(@"modulo nativo ios");
}

inclua o seguinte method na lib Android - android/src/main/java/com/username/reactnative/RNComunicacaoNativaModule.java

import com.facebook.react.bridge.Promise; //comeco do arquivo

@ReactMethod
  public void checkBridge(Promise promise) {
    promise.resolve("modulo nativo android");
  }

no projeto react-native que você deseja incluir sua lib digite o seguinte comando. npm install <caminho do diretorio> exemplo do caminho "../../comunicacao-nativa" na pasta ios apos a instalacao pod install

$ npm install react-native-comunicacao-nativa --save

$ react-native link react-native-comunicacao-nativa

1. In XCode, in the project navigator, right click Libraries ➜ Add Files to [your project's name]
2. Go to node_modules ➜ react-native-comunicacao-nativa and add RNComunicacaoNativa.xcodeproj
3. In XCode, in the project navigator, select your project. Add libRNComunicacaoNativa.a to your project's Build Phases ➜ Link Binary With Libraries
4. Run your project (Cmd+R)<

1. Open up android/app/src/main/java/[...]/MainActivity.java

• Add import com.m3n0r.reactnative.RNComunicacaoNativaPackage; to the imports at the top of the file
• Add new RNComunicacaoNativaPackage() to the list returned by the getPackages() method

2. Append the following lines to android/settings.gradle:

   include ':react-native-comunicacao-nativa'
   project(':react-native-comunicacao-nativa').projectDir = new File(rootProject.projectDir, 	'../node_modules/react-native-comunicacao-nativa/android')
   

3. Insert the following lines inside the dependencies block in android/app/build.gradle:

     compile project(':react-native-comunicacao-nativa')
   

import RNComunicacaoNativa from 'react-native-comunicacao-nativa';

// TODO: What to do with the module?
RNComunicacaoNativa;