gatsby-node.js

const path = require(`path`)

exports.createPages = ({ graphql, actions }) => {
  const { createPage } = actions
  return new Promise((resolve) => {
    graphql(`
    {
      allPostsJson(sort: { fields: published_at, order: DESC }, filter: { status: { eq: "published" } }) {
        edges {
          node {
            id, slug, title, published_at, status, markdown, html
          }
        }
      }
    }
    `).then(result => {
      result.data.allPostsJson.edges.forEach(({ node }) => {
        createPage(
          {
            path: node.slug,
            component: path.resolve(`./src/templates/post.js`),
            context: {
              // Data passed to context is available
              // in page queries as GraphQL variables.
              post: node,
            },
          })
        })
        resolve()
    })
  })
}