How true is that ?
It's completely true. It's basic biology. You get infected by a pathogen, your body builds up immunity through antibody production which recognizes virus particles and destroys them. The only case of someone getting "reinfected" by COVID-19 is if they had the disease once and get infected by a mutated form. Your body will repeat the cycle again producing antibodies against the mutated form.
But did you hear about the news in South Korea in April 2020? T''''''''hey said that those patients who recovered can still become positive again after having a negative result in a tests.
It is still not safe to go outside even if you are a Covid-19 survivor, because there is still a risk that you can infect other people. But in the article, they said that maybe it is a technical error during a test. After a recovery, dead virus fragments can still be there inside a Covid-19 survivor's body and it can reactivate. It can really make us anxious about our surroundings so it is still risky to go outside, so as soon as possible, stay at home for the sake of everyone.
Source: https://www.businessinsider.com/coronavirus-south-korean-reactivated-cases-not-reinfected-experts-2020-4
I also saw that news where a certain survivor of the covid-19 got infected again. I thought that they will be immune anymore because there are now antibodies that they get from surviving.