gatsby-node.js

const path = require(`path`)

exports.createPages = ({ graphql, boundActionCreators }) => {
  const { createPage } = boundActionCreators;

  const loadPosts = new Promise((resolve, reject) => {
    graphql(`
      {
        allContentfulPost {
          edges {
            node {
              slug
            }
          }
        }
      }
    `
    ).then(result => {
        result.data.allContentfulPost.edges.map(({ node }) => {
        createPage({
          path: `posts/${node.slug}/`,
          component: path.resolve(`./src/components/templates/Post.js`),
          context: {
            slug: node.slug,
          },
        })
      })
      resolve()
    })
  })

  const loadPages = new Promise((resolve, reject) => {
    graphql(`
      {
        allContentfulPage {
          edges {
            node {
              slug
            }
          }
        }
      }
    `
    ).then(result => {
        result.data.allContentfulPage.edges.map(({ node }) => {
        createPage({
          path: `${node.slug}/`,
          component: path.resolve(`./src/components/templates/Page.js`),
          context: {
            slug: node.slug,
          },
        })
      })
      resolve()
    })
  })

  return Promise.all([loadPosts, loadPages])
};