Fixed TypeScript 3.7-beta import issue (#622).
Fixed TypeScript 3.7-beta import issue (#622).

ethers-io/ethers.js,ethers-io/ethers.js,ethers-io/ethers.js,ethers-io/ethers.js,ethers-io/ethers.js,ethers-io/ethers.js,ethers-io/ethers.js