gatsby-node.js

const path = require("path");

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

  const BlogPost = path.resolve("src/templates/BlogPost.jsx");

  return graphql(`
    {
      allMarkdownRemark(
        sort: { order: DESC, fields: [frontmatter___date] }
        limit: 1000
      ) {
        edges {
          node {
            frontmatter {
              path
            }
          }
        }
      }
    }
  `).then((result) => {
    // eslint-disable-line consistent-return
    if (result.errors) {
      return Promise.reject(result.errors);
    }

    return result.data.allMarkdownRemark.edges.forEach(({ node }) => {
      createPage({
        path: node.frontmatter.path,
        component: BlogPost,
        context: {}, // additional data can be passed via context
      });
    });
  });
};