The subatomic particle that was discovered by Goldstein was

Proton is the sub-atomic particle discovered by Goldstein.

In 1886, E. Goldstein identified brand-new radiations in a gas discharge that he named canal rays. Positively charged radiation from these rays eventually led to the discovery of protons, another subatomic particle.

This resulted in the positive particle having a charge equal and opposite to the electron. The positive particle was named the proton.