Long-duration γ-ray bursts (GRBs) are the most luminous sources of electromagnetic radiation known in the Universe. Prompt flashes of megaelectronvolt-energy γ-rays are followed by a longer-lasting afterglow emission in a wide range of energies (from radio waves to gigaelectronvolt γ-rays). At higher energy, a new era has started with the detection by Cherenkov ground telescopes of three long GRBs in the last one and half year. I will report on the observation of TeV emission from the γ-ray burst GRB 190114C with the MAGIC telescopes on January 2019. I will then show how the Large size Telescope of the future observatory CTA will greatly improve our knowledge on those sources at these very high energies.